I'll call this bull shit.
Is it impossible? No. But it is almost impossible which means it is practically impossible.
Everybody can create an excel sheet and put random winning bets in it. It is not that hard.
Let the op share what op wants but I agree with you that the spreadsheet can be created unless op provided the real bet details on the site that op used instead of giving the spreadsheet shit. One more thing, it is not just 1 year but 3 years. It's not that simple to do but I can't believe with just the numbers on spreadsheet just as you said it coulr be random.
Let's say he really managed to make a million... He can only prove it if he shows us a screenshot of his bet history. I know that also can be forged but it is harder and we can verify this by contacting the casino. If he cannot do that, I say it didn't happen. If I was a I guy that made $1m out of $5k, I also wouldn't create a thread about it in the dark corners of btt. I would just enjoy my retirement.