labels like Bi and Pan do not have just one simple definition that applies to everyone who uses them. they’re just words that help people express their sexuality/gender identity, of which everyone has their own, no two are truly identical (just like how not all straight people experience attraction the same way)
but generally, Bi means attraction to 2 or more genders (of which, again, there are are a limitless amount, not just cis/trans male/female), and Pan generally means an attraction either to all genders, or to everyone, regardless of gender. but again, which exact definition someone uses is up to them.
is this confusing to a lot of people? yes. the point is, don’t make blanket statements about labels, especially ones you don’t have experience with.
also, I accept that I may be wrong about some or even most of these things, so don’t take my word as gospel. this is just one lesbian omniromantic trans girl’s opinion.
weird that you mention that, rather than the actual rule which makes this impossible, that you can’t normally promote to a king. clearly OP found an exception to that rule though