FWIW I asked my accountant in PT, he’s very used to handling US expats. He didn’t elaborate on specifics, but said that while the necessity to sue was previously true, accountants have access to a way to file from 2023 onwards that doesn’t require paying the tax up front and then claiming a refund with Finanças. I would recommend anyone in this case get good tax representation in Portugal.
Edit: but remember this loophole is specifically on US-sourced capital gains. If you have gains from any other country you will pay the 28% in Portugal.