Both are true. The person grabbing will judge nage by their response to the grab. That was the OP's point.
My point is that the person being grabbed will also judge uke by the nature of their grab. Often people who feel the need to "test" someone in this way don't realize how much they are revealing about themselves.
There is a difference between a honest/sincere attack and an attack that is intended to "test" the nage. I had been chided by past senior instructors for "pussy" attacks and taking "charity falls" and had been also chided for "attacking wrongly" by the same people when I was unable to collude with them. Ironic, isn't it?