I warned clients who claimed an RRC that it was based on what we knew about how much they had received in the first two EIP's, so if IRS had better information they could expect an adjustment.

Then when clients told me the RRC had indeed been adjusted, I explained to them that the notice they received did not comply with the law that IRS must follow when changing what is called a "math error." So, they should expect a follow-up letter informing them of their appeal rights.  For those who try to keep up with current events in the tax world, this was general knowledge.  

Now when they call, I just remind them this is the letter where IRS admits, very obliquely, that they screwed up by not telling them what they could do if they disagreed with the first letter.  And of course, if we had good reason to disagree with the RRC adjustment, we have already notified IRS so the ball is back in their court.