I don't know enough history here. The current Moose docs say "Moose is built on top of Class::MOP" so maybe there was a different MOP effort that succeeded? That MOP is probably closer to 6Model than Moose itself.
Moose did take inspiration from the object model designed for Perl 6, but it grew out of attempts to implement that object model in Pugs, not Rakudo. You might even say that it was the first full implementation of the Perl 6 object model.
I think my original point, though, holds up: One of the actual delivered achievements of the Perl 6 project is a sophisticated flexible object model, now in production outside of Perl 6, and also the basis of deeper (re)design within Perl 6.