If they didn't specify how they're determining a stock price to derive a # of shares from, or if they actually specified a number of shares rather than a dollar amount, then no, that's not normal. Get out and go somewhere else that doesn't play stupid games.
they changed the avg in their favor afterwards bc we joined on covid dip..
I do not think this is normal and appropriate. The board would have no problem paying you less if the stock declined.
Management that goes back on its agreements is not a management that you want to work for.
Your current employers demonstrated that they are not willing to honour the spirit of the original contract they negotiated with you. Sure, they have some clause such that RSUs grants are awarded at the board's discretion, so perhaps they're off the hook legally. But similarly you can just terminate your employment and stop working for them if the deal is now not attractive.
That said, if you are still getting paid more working for this company than other employers, quitting for another job might not be your best move.
Can you compare what you are getting paid with other employees in similar roles who joined at different times? It is possible you may be getting under paid anyway.
I work for a big company that has a reputation for doing the right thing, which might have been true in the past but doesn't seem to apply now. I have seen them change grade structures, change promotion amounts, and change the pay/bonus structure all to the employees detriment. They always try to put some positive spin on it. I remember I brought up the topic of a raise with one boss because I was low in the pay scale for that grade. His response was that this was a good thing because it gave me room to grow. Seriously? I'd rather be near the top of the scale and not grow very much. Same thing for when we used to be able to count on 3 10% promotions but then they changed it to 4 7% promotions to get to similar compensation (it's actually below because the bonus isn't as good, not to mention it takes years longer to hit that 4th level).
EDIT: This is very unusual for large public companies. This is the first time I have heard of such a practice.
This is just another one of those tricks that companies do to try to boost your base compensation, but without putting the actual money in. Cash will always be king, always prefer it against RSUs.
Perhaps you should look at the big picture. Are your earnings above average? Was the stock grant the only reason you took the job? If you start legal action or make a lot of noise, your career will probably hit some roadblocks at that company and possibly others if the news gets out in the open.
If they won't - you have option to summon legal help.
Yes, if you are a productive worker for a generous employer they will handsomely reward you for your particular contributions, as well as give across-the-board increases in pay and perks, and it will exceed everyone's expectations.
I would start interviewing elsewhere immediately.