It's typical for unvested RSUs to accelerate and vest on change in control. Based on the 10k, there were about $2.2B worth of unvested RSUs at the start of 2022. Musk's $44 billion likely covered some or all of that (or whatever % vested and/or wasn't already forfeited) so it's unlikely there is any real savings. Unless some of those RSUs converted to Private MuskBucks, then he may be saving something.
Allegedly Twitter employees with unvested RSUs were scheduled to get equivalent cash payouts on the same schedule as RSU vesting. I don’t think this will solve his debt problems, but it’s gonna move the needle.