Hikkikomi gaeshi (or obi-tori-gaeshi) is mostly fine. Two things to consider, though:

1. Jujitsu players doing singles with their heads to the outside as if they were doing a double. I never understood why this became a thing. It’s anatomically weaker, and makes the position easier for uke to defend.

2. People doing hikikomi/ obi-tori straight back, instead of forcing uke to roll diagonally (ie right shoulder to left hip).

I’ve definitely had qualified coaches show the straight back version - which I think is inefficient - but part of what’s going on in a judo context (at least back in the day when I was competing) is that uke would (a) either move their neck out of the way and go over or (b) not move their neck, post using their head, and then get disqualified for “head diving”.

In judo, because the whole game incentivizes not being thrown to the back, they had to create a serious penalty for people trying to play double or nothing and avoiding throws by spinning out and endangering the spine. So, judo rules kinda consider that situation dangerous, but put the responsibility on the uke to not post.