Could this happen to the backdoor Roth? I know they've clarified the "mega" backdoor Roth, making it perfectly valid, but AFAIK there hasn't been word on the backdoor Roth.
I'm thinking of cases like tax credits for R&D, where a company claims the lab janitors salary because the lab isn't going to clean itself, but the IRS decides that salary doesn't count as a research cost. The law from congress doesn't usually spell such things out. Or it says "necessary personnel" but is a janitor necessary or not?