In practice, the chances that N programmers with follow the pretty comment convention of a given file approach zero, as time passes.

Splitting into files is an approach that is easier to lint against (e.g. max 500 lines - a best-effort mechanism to foster SRP).

And it's not really problematic after mastering a few key aspects: jump to definition, and more interestingly Peek Definition.

It's also important to not traverse files top-to-bottom (which yes, is very tempting).

Optimal code traversal is tree-like, you jump from definition to definition, skipping over the irrelevant, and gathering necessary info on demand.

The file/line location of a function becomes irrelevant.