An uke that holds relaxed is like my son, daughter or wife holding my hand. There is no intent, and with no intent there is no need to protect yourself. There must be action to cause reaction. A parked car poses no danger, yet a moving one does.
I'm not sure I understand exactly what you mean regarding holding in a relaxed way. Would you be willing to explain a bit more?
My understanding is that relaxed grips like that of a baby, for example, are ideal because they allow for greater diversity of pathways for the intent to manifest through. I would agree simply standing there holding onto someone without any further
intent isn't very good...if anything, it seems to invite a strike to the grabbing hand so nage has less dead weight attached to the arm/wrist.
A parked anything
poses little danger unless it somehow has greater inertia and you smack into it. And once you've smacked into it, better hope it doen't start rolling on top of you or, still connected, move you somewhere you don't want to go.