Definitely still valid. When I trained as a tax preparer for the VITA program (which involves training specified by the IRS), this was a key point of the training. We were also told that information from clients was confidential and we couldn't report to anyone outside the IRS that someone was earning money illegally. The software (paid for by the IRS) even had built-in workarounds for reporting income for someone with a fake SSN on their W-2 because they didn't have work authorization.

I did this for multiple years, and some of the volunteers had been doing tax prep for over a decade. The same clients came in year after year. If we couldn't guarantee that their tax information was safe from ICE, they would definitely have stopped coming.