I think the confusion may be that you commented on freeway safety, whereas the comment you replied to discussed highway safety. Freeways are limited access highways; not all highways are freeways.
'Freeway' is a regional term, but the Federal Highway Administration describes them as limited-access with directions of travel separated by a barrier.
Yes and I believe when OP said highway they meant it colloquially, as in a freeway, hence using that term in my reply. A highway wouldn't really make sense since it encompasses just about every road, as you say.
Nobody is cycling on either unless there's dedicated infra anywhere even the slightest bit urban. In rural areas cycling on a limited access road is generally "fine"
https://brilliantmaps.com/wp-content/uploads/big-fast-road.j...