I’m not entirely familiar with this bug, but it sounds like there’s something else going on for a NVIDIA proprietary driver env to affect anything outside of that.
If Steam or something else does a check for that specific env regardless of GPU and then does something based on it, it sounds like understanding that something could hint to a different thing causing the issue (I’d search on Valve bug trackers with that env).
Could also be something like that large text string causing a race condition or extra spacing in a command syntax somewhere; Flatpak and Steam do a lot of stuff 
(especially pressure-vessel stuff)