The best thing you can do is get to the finish line, get the offer sheet, and demand that your position as a full-time remote worker be written into your agreement with the company.
FWIW I know someone who did exactly this with a defense prime, and the crazy fella actually won the battle with HR when they tried to bring everyone back into the office.
Worst case scenario, they say "no," you decline the offer, and you've sent a clear message to management. It might feel like a few hours of wasted time, but we as industry practitioners have the power to make this a normal interaction between a prospective hire and a stubborn corporation.