Look, we're just arguing semantics here - I don't know why it's so important. Yes, it's fair to say that Bo Katan had a major role in season 3 of The Mandalorian. You might refer to her as a "led," a "supporting lead," or even "supporting." It's not that well defined. To me, she didn't steal Din's thunder so I don't really see it as an issue. Even if the producer says she's a "main protagonist" that doesn't mean that she is or is not a lead. Sure, both of htem got a lot of screen time, but it's telling to me that the final shot is of Din & Grogu.
Here's an explanation:
https://www.liveabout.com/difference-between-lead-and-supporting-actor-2428097
What's concerning to me is how you seem to have a problem if a female character gets even the slightest amount of credit over the male character. You don't complain if another man upstages the lead. How dare a female supporting character not be completely outclassed at every turn by the main hero, right?