Does taking this example and extending it to the limit answer your question? There is a reason we don’t have a single file called program with a million lines of code in it. Google studies on module size vs code defect rates for more empirical numbers.

The limit you're replying to is files which are each tens of lines long. At that point, the cognitive overhead of switching documents is larger than the benefit of a compact object to reason about.

(Personally my threshold is around 2-5 thousand lines per file depending on what it is; but that's me working solo, obviously I'll follow whatever standards any team I'm in gives me).