I'm certainly not saying that uke should be going through the motions or giving away their balance. That's not what I mean at all. What I am saying is that if nage is practicing shomen-uchi ikkyo, then uke should be trying to hit nage in the head. IMHO this is not particularly 'aiki'.
Sorry if I misunderstood you. I agree with you, uke should provide an “attack” that is on target and realistic enough to provide a challenge. My point was that the same mind/body principles apply whether you’re defending or attacking. Uke should move from the center, in a connected way, and applying aiki principles. And if uke is the senior (aikido has this backwards imho), s/he would feel whether the nage is doing it right or not and can offer feedback.