This is not entirely accurate. You can use Starlink in RV mode on a vessel, you just don't get the higher throughput and availability of having two antennas and the orchestration for them. There is some nuance.
I'm pretty sure that Starlink will start identifying and dealing with nautical customers who don't use the nautical package. Right now, it's like a legacy mode. But after enough nautical antennas have shipped, they're not going to deprioritize the $5k/month customers
https://youtu.be/zN8ECQrot8g