Please change the description, it's very confusing. It says 21+ , but MN adventures are actually for 20-22. I have been training my team for days on those hard adventures to start it with 24 lvl characters, but it's impossible. I'm disappointed.
They probably don't read this board very often. You can ask a mod to move this thread over to the bugs board. And it should say "21-23".
It also says 17+ and 18+ on the L17 and L18 modules, and like any module in the game you are capped at 2 levels higher than the adventure level. I see no inconsistencies.