I think that for so many who practice aikido, discussions of "extension of energy" and the like are like critiques of the emperor's new clothes. That is to say, you're trying to understand the nuances of something that may be a metaphor, may be a colorful way of describing a series of mechanical actions, may be literal truth...could be all of the above. Maybe. I don't think it helps, though, to get engaged in a discussion of whether the emperor should be wearing that shade of blue, when you're not really sure if he's even wearing clothes. If you're not seeing the clothes (either because you're not able to yet, or because the clothes aren't even there, doesn't matter which), then don't get involved in a fashion discussion, that's my advice. Don't get involved in a fashion discussion, and also, don't waste your time trying really really hard to see the clothes. If they're there, they will become apparent in due course.
Meanwhile, practice. Don't worry if you don't have the grand unified theory of energy extension. You know enough by now to do good practice, so concentrate on what you do know. Focus on basic mechanics: "energy extension" can't make up for a sloppy stance, badly distributed weight, hands held carelessly, pivoting on the heels, etc. It's my personal belief that good basic mechanics are a prerequisite to anything like "energy extension": you can't go off into a room somewhere and gaze at your navel until you have an "energy extension" breakthrough, and then bazing, all your mechanics are superb. Rather, having bad mechanics is a perennial obstruction to any breakthroughs at a higher level, and having good mechanics clears the way so that such breakthroughs can happen. They don't guarantee that it will happen, mind you -- that's where patience comes in. Focus on doing the things right that you know how to do right, be patient and content with striving for that, and let breakthroughs happen in their own good time. Personally, I've never experienced or noticed a martial arts breakthrough in the moment, as it were. It's always a case that I suddenly notice something that's been there for a while...never a case that I do something right for the first time and say, "Aha!"
Mary, I'll dare to put words in your mouth, this sounds like a shaddup-and-train.
But, what's good mechanics? Is it possible for someone to really have them after a year of training? And if, perhaps, good mechanics are to be regarded as what-sensei-says, and shaddup-and-train is to be regarded as do-what-sensei-says, but when sensei can't point out what's going wrong, ain't there a problem there?
Could it be that good universal mechanics that apply to all movement is the entire problem of this whole martially-artsy-fartsy endeavor, and that if they were so basic that you already had them, and it was just a matter of applying them, there wouldn't be much point in training a lot anymore? If you only focus on what you think you already do right, what're you gonna learn?
What if it wasn't right, what would you compare it to say it wasn't if that's all you did? Maybe it was right in only a limited context, and then going off into a wider movement context, suddenly everything you did before was wrong and needed to be discarded, hmm? Could focusing on too limited a set of "basics" actually force one into the rut of local maxima, a "flavor" or perhaps "smell" of moving, rather than helping to discover more globally applicable ways of moving that are perhaps less, well, odoriferous in nature?
A decade in a hakama left me feeling pretty naked, and I guess, borrowing the last metaphor, pretty "flavorful". But being isolated in the grand aikido nudist colony you tend not to notice.
And geez, once I learned that martial artists could actually wear clothes, I had to throw out entire wardrobes ten times over in the span of months just because one shade of blue somewhere was not quite right, which usually turned out to be that it wasn't in fact that the shade of blue on the shirts and pants weren't matching, but that I was missing pants, which was why they didn't look very blue, or maybe should have been wearing a turtleneck, or something that didn't make my ass look so big, or maybe I just needed a nice belt to go with it... But, hey, Mary, if you like walking around in the buff, no complaints from me. I'm a man, I can take it.