As someone said, it was in peer review for a year.
That means it could not have been compared against stockfish 9 or 10 - they were not released yet.
As someone above points out, they used in-development stockfish versions as well (2 weeks before sf9 was released), and from what I can tell, they used the newest version they could have.
If you have some good data that means you can make this statement, can you please cite it?
Otherwise, can you please not make claims of bad faith?
That said, I've checked out a few old versions of Stockfish (including the exact commit they used) and analysed the games in Table S6 in the paper. Stockfish still spots multiple blunders in its own play. Obviously these things aren't entirely deterministic, but it seems unlikely there was time trouble.
And again, just to be clear, there's little doubt in my mind that AlphaZero's evaluation of any given position is better than Stockfish's or anyone else's. I'm not even saying it can't reliably beat Stockfish. I just find it sad that the evidence of its overall strength continues to be wobbly.
If you really feel like their original setup handicapped stockfish, it seems like the best way to know would be to have that setup play your preferred setup and see what the difference is.
He says he's analyzed the published games, and found that Stockfish finds obvious errors in the way that Stockfish was said to be playing. Unless he's consciously lying about this (I'd guess unlikely?) it's not libel. And if it's true that a correctly configured Stockfish doesn't play the way it was said to play, this would be a strong indication that either intentionally or accidentally, it was not a fair playing field.
Anyway, if your point was that it might be more productive to be more polite, sure! But one might say the same about accusing someone of slander.