There are swing away ones that have the same caged design feature and still allow access to the rear without lowering a 100+ pound tire to the ground every time and then have to lift it back up.. I have just never understood this design as a practical solution.
While that's true, the swing aways you mention (and on your Jeep) transfer 100% of that weight to the body/armor mounts. If you drop off a ledge and it catches on the tire, that's all in the body or armor. They look great, are super functional and I do like them.
However, with the older YJ/TJ style, it'll transfer the load to the bumper(and frame) and body/armor. Also I'd believe the load to be less, as there is no drop off a ledge from the bumper to tire (shock load), but a glide from the bumper to tire carrier.
I'm no engineer. But I'd run one of two things. Tire in the jeep and no hang over the bumper or a GenRight YJ/TJ style carrier to let the rear end slide over ledges.
I've seen several jeeps run a setup in the hitch mount that is a square tube that sticks out to slide off rocks and deflects contact from the tire. I think it works, but it's not what I want on my Jeep.
You're right, you're picking up a heavy spare and this style tips down in front of the tailgate and is in the way. On my 2dr I don't need that much access to the 'cargo' area. I'm glad I read this thread about flex issues. I'd have built my own carrier but seeing this, I don't know that I will.
Not the best photo, but my YJ has metalcloak corners and i built this carrier on to whatever tube bumper was on there when i bought the jeep. I haven't completely loaded the rear end of the Jeep on the carrier, but it's plenty strong (and heavy.)