The seat back thing is the one hack stand-up bit that I've never seen fully explained.
Sure, trays up makes sense, but I can't think of the accident where that kind of good posture is going to be a big boon.
Or maybe it's just a holdover from flights and classes that have fully reclining chairs?
Planes taxi on low engine power, though sometimes they use special vehicles (massive tires & very powerful engines) which push/pull them by the nosewheel (kinda like a tugboat).
In an accident that lowered tray table would probably break your ribs and your reclined chair would increase your whiplash and break the neck of the guy behind you.
The latch on the seatback is strongest upright position.
Yes, because of prevailing winds and where the rich people live, flying into, say DC from Boston, will follow the same route and bank the same way most of the time.
Good answers, thanks!