The only altering that was done was adjusting for error. Which can happen. No one is holding Trump responsible for those numbers either, but rather his clunky messages during his final year and the first year of covid.
The final number was in office before January 20 was 392,428, which is most definitely close to 400,000. Especially if you round to the nearest hundred-thousand.
It is still being updated, because we’re still in the middle of a pandemic, so of course it is still being adjusted. Usually upwards. Very rarely downwards.