Very fair question!
Part of what we get into here is training paradigms. When I'm working on pushout with someone who is new, I go back and forth between offering muscular resistance (so they have something they can push against/into) and offering frame resistance so their eyes can bug out and they go, "What the.."
Pushout is a very limited environment however and it assumes a certain training paradigm.
In a regular Aikido class, I just tank. I go with whatever the instructor showed, and I go wherever my partner points me, and I make a big splat. I don't do many Aikido classes, it sucks for me, I don't get anything out of them and all my partner gets is reinforcement of bad habits. What good does that do anyone? It's emotionally draining, and very boring. It's also not aiki, nothing to do with aiki. It might be aiKi (as I've laid it out based on the modern interpretation based on Kisshomaru Ueshiba's "The Spirit of Aikido") but I have absolutely no interest in that.
Aiki, is REALLY hard! I don't think you can even do aiki (as I use the term) without the old 'baseline skillset'. So what to do with new people? That's kind of what we're working on now and we're kind of blessed in that we (meaning Icho-ryu/TNBBC) don't call our selves Aikido, but prefer aikibudo (or just jujutsu). Anyone watching class can say, "That's not Aikido!" and we would say, "We told you that." So beginners work on tanren, ukemi and judo throws. Those three areas work to reinforce each other and build someone who is ready to start learning aiki. I should point out that I don't consider myself to be a master of any of this stuff, most of what I do falls far short of what I would consider true aiki but I also really feel that I'm sneaking up on it. I'm kind of like lone blind man walking around feeling an elephant and describing what the elephant really is. The longer I circle, and the more I touch, the better my mental image is going to be.
re: pushout: That's how it has been for me, I guess I just never saw it as tensing up as being the method of dialing it back, because I'm the guy going "what the !!?!?", but it makes sense.
As for the aikido, maybe it's different for me becuase there are so many similarities between what I've done there and things I'm learning on the outside. Now don't take that to mean "we were already doing this", but there's just so much conceptual overlap that often times it's not hard to take what little I know and make a suggestion here or there and feel it make a difference in what someone is doing. What will that amount to in the long run? I don't know, but I'm not really worried about it. I don't expect everyone to care or be interested on the same level that I am. The more casual people will benefit from that and the more serious people become the ones that help take it to the next level. I enjoy both sides of it.