Is Babylon spreading my religion?

I see a babylonian missionary approaching my borders.

Here's the thing... I have converted all Babylonian cities to my religion, including the capital. He has "happily adopted" my religion, and he doesn't even have a pantheon!

But he has a missionary. Which means, he got 200 faith together, and pumped out a missionary, but somehow decided NOT to start a pantheon? Presumably since all his cities are my religion, that missionary is on the side of right and good, and should be encouraged?

Does this make any sense at all? If not, what's that Babylonian missionary doing?

Does the AI not form pantheons if it already has a religion it the majority of its cities?

Alternatively, are all the pantheons already taken?

Perhaps that missionary was freed from barbarians rather than domestically produced? This could be possible if your religion was successfully spread to another civ.

1. Are there enoughs Pantheons founded to fill in the maximum available religions (7 max religions in a game require at least 7 pantheons) if so, then chances are you or someone else with religion has enhanced it, blocking the ability to spawn/create further pantheons.

So, I captured one. It's not my religion, it's another civ's he had been at war with way way way back at the early part of the game. He must have captured it, and just decided to hang onto it forever and ever.

The AI will do that, paying gpt maintenance on a captured missionary that is useless to it.