Neither did I - try re-reading it.
Chris, I wrote more than one sentence. If I was to direct a communication to you on how you read what he put then it would be more as follows:
1) I don't think he implies that the attacker in motion is unstable.
2) I don't think he implies uke being motionless in front of you is a barrier or is preventing you from doing anything. No different to a lamp post really.
3) He implies what I said in the last sentence, ma ai and de ai. He implies in my estimation Aikido blending motion.
Only he knows. I may be completely wrong.