To that end, Disney is trying to push its hard core audiences into purchasing its other media - the TV shows, the novels, the comics, etc. When there were only the comics and novels, I read the novels. I don't have much time for that anymore, so I'm not keeping up on all of it like I once did. Most people don't have either the time or the desire to go through all the minutia of Star Wars media, so tossing in Maul didn't make sense, like you said, while to others it just confirmed that the timeline was sometime after the midpoint of the Clone Wars and prior Luke meeting Kenobi in Ep. IV.
Solo, they made a quick reference to Aura Sing, a bounty hunter from the Clone Wars cartoon series. If you watched it, it was a quick nod to you. If you didn't watch it, it's a nearly throwaway line designed to set Woody Harrelson's character as a tough guy. That's how these references should be handled, not like Maul.