Just to make sure, it's done by opening the pip-boy then forcing the game to pause (ex. alt + tab).
I really don't think it has much use, seeing as you can't interact with anything, but it is really easy to execute.

Don't know if this is new, but I've found a way to pause the game while still able to control my character. Everything else is still frozen, but you can move around. I've also managed to reproduce it multiple times.

Video:
https://drive.google.com/file/d/1btawATk0IVuEZvxDTWyThd_vhISN_owx/view?usp=sharing