Baldur's Gate 3 makes a lot of attempts to look for files that don't exist.
It seems as if almost any given file access attempt first tries to load the file loose from the disk before then checking in the PAK files. I guess so that loose files get priority and can override those in PAKs when loaded?
With how many files the game loads at basically every loading screen I wonder if there'd be any noticeable benefit from disabling this and making it so that it prioritises PAKs instead. Probably not much, I don't know how expensive of an operation this is.
Also for some reason the game actually refuses to even make it to the splash screen unless I've got ProcMon open. Maybe it's just coincidence.