You receive money when it becomes available to you to spend. That does not necessarily mean that a withdrawal can be said to occur on the day you request it, even though the requested funds are no longer available to you to invest.
I suspect that somewhere in the broker’s fine print there is a statement about transactions taking a few business days to settle. As a result, if you try to claim income in a different year then is shown on the 1099 prepared by the broker, I think you would have a very difficult time making your case before the IRS.
To be specific, the IRS will be quite happy to allow you to declare additional income and pay additional tax for 2021. If you then fail to report the income for 2022, they will assess tax and penalties. If you insist on pursuing your case through the courts, so much time will pass that if you lose your case, it will be too late to amend your 2021 return to remove the income, and so you will end up paying double taxes on your withdrawal.
If you missed your RMD by a couple of days, you may be able to request a waiver of the penalty for cause. Otherwise, I would not recommend disregarding the date provided by the broker and substituting your own date when reporting income.
