Fire and Brimstone Hell is also commonly believed, but not actually in the bible, if I recall right.
Most of the punishment around Hell in the Bible is less about Hell itself, and more about not being able to enter Heaven and join God, and all of that, as oppose to Hell itself being punishment.
I feel like it’s more the opposite problem. For the parents, trans people are a vague boogeyman. They’ve never meant a trans person personally, and they’re constantly told that trans people are just waiting to jump them in the bathroom, or at sports, or all sorts of other things, so they’ve never had to contend with someone they know being trans.
If it was simply stress or threat to the kid, it wouldn’t really explain the reaction to disowning them, since most of those aren’t about the treatment that their kids would receive for being trans.