I have no science to back this up, and I may have said this on your
original thread, but I really don't think aluminium drop-outs and carbon
forks were designed to be rigidly attached to a rack that essentially doesn't move.

Do they have racks with spring-loaded or rubberized attachments that would provide some "give"?

If you consider what forks are designed for -- it's to have a wheel in them that flexes and turns, therefore having plenty of 'give'.

Anyway, my two cents.

I rarely drive with my bike in the car, and if I do, I either throw it in the back seat with the front wheel off (obviously ), or take both wheels off and chuck it in the boot.