As I don't own a PS4, could someone explain what you mean by locking the UI? I'm sure it's something I'm already aware of but haven't heard that term for it. Or it's just a dumb moment for me. Those do happen.
Not sure if MS already changed already, but last time i checked XBOX1 had to way an update to fully download and install before playing game or being able to do anything with the console, we had this in PS3 and it used to be a huge pain in the ass wait to do anything else.
The PS4 update, upload and DL system won't free and say wait for something to fully download or upload in order to do anything, so you can play any game watch any video, browse anything, rune any app while anything else is download or uploading, i think its like p2p system or something.
The only times where you have to wait is when copying files from the system into a USB port, rendering videos edited on the console, trimming vids.
But when a new update for a game like a patch drops, we just continue to play the older version until the new patch is ready to install.
I felt like MS was really far behind in this aspect, and was really hoping they changed this with a future update, it was so 2013 lol.