According to actual IRS guidance and law taxpayers data is Sensitive But Unclassified (SBU) which means it’s on a need to know basis. I can’t access my own data for instance or those of anyone I know just because. The only time I access data is when I’m resolving a tax matter. I doubt they have any real need to access it. Also there is a law called UNAX which I’m sure Musk will entirely ignore.