I can speak to DIY versions and doubt the real deal is effectively different...
They are "safe" there are no sharp edges and you can walk on them, but it's not comfy. As for putting a knee on one when crawling in the boat, it's painful, but not more so than frame rails and other hard objects you have to contend with. I thought about insetting mine into side deck, but seeing the side mount versions I could easily go that route! Too many options I guess.
Anyways long story short they are not particularly hazardous.
Yesterday's gone on down the river and you can't get it back. - Agustus McCrae