So, yeah, kata means you have to work with the situation and the abilities of your training partner. If they can't unbalance you, give up enough so they can unbalance you by doing the right thing (whatever you were training). As they get better, give up less. Same with leaving your arm hanging out there--leave it out long enough for them to work through whatever they need to. As they get better, you should move more and more to real time. This is something you and your training partner can and should negotiate in the moment: "Slow that down, and don't go so easy on me. I'm not really getting the kuzushi." "Speed that up. Let's see if I can handle it if you rechamber the strike the way a boxer would."
Excellent rendering of what Maruyama sensei referred to as logical resistance. Thanks.