I'm not sure I follow on the Fallout 4 front. Recently ran through it again, modded to high hell. Installed Vortex from Nexus mods, it auto installed all my old mods I had subbed to from Steam, I queued up a bunch of new ones, it installed them for me, I click "run" and bam. No hassle. Playthrough ran about 4 weeks and not once did any update break things. You're right about the forced patching, but I haven't had a rough time with mods in forever. Granted, I only run mods on FO4, Skyrim: SE and MHW. I don't use the Bethesda store at all.
If he didn't want the game to update he could just have set Steam to offline mode and made sure the game was set to 'Update only when I run the game'.