What are the odds that he calculated a certain number of bytes, and exactly one other employee had sent a file to the printer that contained that number, but it was just a coincidence? If the method indeed doesn't work (as you suggest "is possible") it's impossible it would turn up a false positive, only a false negative.
It's also possible that he calculated the number of bytes, searched the logs, didn't find anything and then tweaked his numbers until something matched. And then fired that random person to make a statement and lied about how he found out who to fire.
This approach would work in isolation, but by failing to find the true leaker would result in them being empowered to leak more over time. Is there evidence that Tesla has a lot of regular leaks?
almost as good as the odds that he got something pretty close, then changed the details a bit to fit the narrative.
or, he stayed up for two days until he got it exactly to match by tweaking his approach a little at a time, and actually matched it to the right person. Honestly, he seems like he'd do this.
You wouldn't do that though, would you? You'd type the thing up, print it, see that the printer received a 4.7 KB (or whatever) doc and look for a 4-6 KB doc the week of the leak, and then you have 100 documents to go through, rather than 100000.