Moving the Darth Maul cold open to the end of S1 not only would be confusing from a timeline viewpoint, but also because the Nightsisters arc already ends with a pretty unambiguous Maul tease. Jumping from that to seeing Maul in the flesh would feel jarring and make the scene quite redundant to work as a post-credits.
Good point though about the mandos- they probably wouldn’t even know he he was. That said, is it common knowledge that his species is largely unknown?
Zabraks seem to be a pretty abundant species across the galaxy. In fact there’s one episode where the Jedi discuss Maul’s homeworld and they imply that is common knowledge that most Zabraks come from a planet called Iridonia. I guess it is the sight of the Dathomirian patterns, missing limbs and lightsabers what makes Vizsla wonder about what they are.