I think adding something when nothing is known is not helpful, sure, but adding something when you *know* someone was not buried would answer a question. Especially if the goal is to have an entry on every profile (as stated in the project page). I think the Cremation and Buried At Sea cover a lot of situations, but what about folks who aren't either of those, but aren't in an official cemetery either? ("Uncle Bob was buried out in the back 40 under the oak tree") Also wonder what would be suggested for those who had no remains to be cremated/buried due to natural disasters, war or accidents?
As for FindAGrave, I think they just want to have a memorial for someone, and it's easy to create there. Not a lot of validation checks going on, obviously.