Despite OP's abject lack of actual computer knowledge, the answer here is 'yes'.
UE3 had a bunch of proprietary licensed tech that Epic weren't allowed to ship with 4 when they open-sourced it, so they've had to build their own lesser equivalents that can be released to the general public.
It's been a few months since I actively followed UE4's release notes, but to my knowledge this process is still ongoing. 4 will eclipse 3 eventually, but making free-and-open-source equivalents of popular game engine middleware takes time.
Yeah, Epic have some funny priorities when it comes to notable features like that.
You can't customize the main camera's projection matrix because they reserved it for implementing part of TAA, so even if you don't use TAA you're being blocked from a useful feature because someone on their tools team thought that smeary-blurry AA was more important than the fundamental rendering pipeline
Not if there are lawyers telling you that part of said tech has to be pulled out and replaced between generations.