Sure, but only if you're just talking about one small subset of how the yari was used, ignoring the vast complexity of the weapon as it was made and used. I think what people are pointing out is that it misses a vast domain of how the yari (as an example) was used historically. It is a gross oversimplification. But I'd agree if you're only talking about one movement -- the thrust. But even within that thrust (say you're using a jumonji yari) there's a lot more potentially going on.
If you're only focusing on that in exclusion to anything else and not making any points about anything else such as the larger nature of the diverse weapons systems of Japan, well, fine. But these weapons didn't appear out of the blue. They have a history and an evolution. And there are vestiges of the evolution still contained within. Also, remember that in many martial arts styles there was a consistency of training that reflected that they wanted what worked with the stick to also work with the yari (as an example). So you might see a movement with a jo that looked odd to your eye. You'd be missing the point. The movement is to learn to move a certain way so it would be effective if you're using the jo *or* the yari. You train to be consistent across "weapons platforms" to ensure proper mechanics. But that's probably another post there... Back to yari -- what I wanted to post on having long been a fan of antique yari blades.
Many in the world of nihonto collecting feel the word 'spear' is a misleading word when used to describe the Japanese yari. Most collectors just call them yari knowing full well that saying spear just muddies the waters. Spear brings up images of a stick with a sharpened head and that image often leaves people with a very limited idea of both how they were used and how they might look. In most cultures the spear is just wood with a sharpened head - one of the simplest of weapons. The spear can be used as a thrusting weapon and it is often also used as a projectile (think of a javelin). The Japanese yari is vastly more complex (leave it to the Japanese to take something to the Nth degree of complexity and refinement).
Yari "points" are incredibly diverse reflecting the variety of ways they could have been used with the notion of a 'spear' being only a subset. Even the smallest yari is more than a sharpened point -- they literally have a "ha" (edge) running on at least 2 sides. The smallest of them have a few inches of cutting surface for cutting movements. But beyond that there are a huge variety of yari that are vastly larger, longer, many with multiple, complex blade surfaces. In this day and age of google I'll let you guys do the footwork, but look up the varieties of jumanji yari for example. Within jumanji yari there are probably another 20-30 subtypes of different blade shapes, sizes, proportions, etc. These are yari with cross blades that are incredibly complex and sharpened along *all* those edges. It can cut on the thrust, on the pull, on a cut, heck, I couldn't figure out how the heck the polisher even manages to polish the (literally) bloody things.
And if you want to see some really interesting shapes look up styles like these... Tsukagata. Kuwagata. Tsukikami. Karamata. Kakehazushi (variation of jumoji). Katakama. Or for a really bad nightmarish style, look up the Futamata yari which is actually two very long "katana-like" blades oriented such that the nakago align creating a large "V" going forward with the sharpened parts on the inside of the 'V'. "OFF WITH HIS HEAD!" Yikes.
Sure, they're thrusting weapons. And cutting weapons. And some could take the legs off a charging horse. Some could do massive damage being pulled back. Some even had secondary blades or guards mouted 2/3rd down the pole. All these variations meant a great deal of variation in how they were used. They were certainly not weapons limited to our simplistic notions.
And I've not bothered talking about all the types of ishizuki you'd see on the various Japanese pole-arms, some of which were made to clearly leave a mark on your forehead (over the skull fracture underneath). I remember one I had for a while that I pulled off a really nice naginata. Sharpened point of iron that looked like a hershey's kiss if that helps with the imagery. The thing was hefty. I remember mounting it temporarily on a pole I had and thrusting a tree in my yard. Amazing the damage it could do. I didn't try using it for a strike as it wasn't attached correctly, but imagine having a heavy piece of iron on the end of a long pole hitting you under the chin in a hard rising strike -- soft food forever.
The point is that the yari is a very complex weapon and the usage would vary depending not only on the yari itself (jumoji vs. nata yari for instance) but also depending on the training of the person holding it. Sure, you can focus on a very tiny subset of how the weapon could be used then make some observations about relationships. This is taking this to an extreme, but that would be like saying that a gun can be used to knock out an opponent with its heavy barrel (which is true of course) and building up a nice weapons theory based on guns being a bludgeon. Of course it *can* be used as such, but you're missing a heck of a lot of details about the way a gun works.
FWIW I just remembered that the Northern California Japanese Sword club has a page on Yari on their site. Just fwiw. They list a few of the common yari shapes showing proportions quite well.
Northern California Sword Club page on Yari.
They're a great club, btw. They put on the best sword show in the US IMHO in San Francisco every August.