Where are the Dark Menhirs during the Grandmaster Battle?

Well, if they're just meant to be an obstacle, they wouldn't really have to move. It's almost like her version of Puppet.

You can't have a map object summoned by another monster, and you can't get a monster to move like one either (back and forth in a specific pattern), and I doubt they actually want the Menhir to move erratically like a monster. Because, well, then it could be lured, and that would be even weirder.