How likely is it that there would just happen to be a file with exactly the same wrong size in the printer logs?

I‘d say if the letter was short it‘s pretty likely.

Maybe there was few % error but no other candidate.

Which printers in that timeframe ever directly printed word files?

It would be the resulting spool file that gets measured, not the source Doc file.

they probably narrowed it down to one person and approached them with the logs and "admit and be fired or don't admit and legal (and all the bad/expensive stuff that comes with that) will be engaged to get to the bottom of it starting with you".

You can also easily narrow it down to a time period. Find out when leak occurred and then look at prints shortly before that.

Way to show your bias with shallow thinking.

EDIT: Read the link. Musk says he sent the letters with different spaces. The leaker would have printed a single letter. Since Musk has all letters, he need only match up printer logs with the sizes of the letters.

If it was converted to Word, then assume the leaker would use defaults. Why would they do anything otherwise?

This just shows that you didn't read the link and reacted based on your bias.

EDIT2: Keep those downvotes coming you biased people.

Two different leaks. One was a printed word file. One was a double-space-encoded email.