Thats a complicated thing to say because the ST functions as a real religion in the US which is the basis for why they’re able to challenge things in court. If they didn’t qualify as a sincere religion their mission wouldn’t work, and that “sincerely held” qualification is actually challenged in some cases. Recently this qualification became an even bigger deal when people claimed they had religious beliefs against vaccination. In the past its been applied to people challenging the draft on behalf of sincerely held religious beliefs.
I don’t think they’re a religion like Christianity though, maybe a pseudoreligion or civil religion.