By HoH:TL p.96f Mutantes, Triceres' Muto Vim metamagic - that is, all ArM5 p.159f Muto Vim but Wizard's Communion - was hidden from the Order, before his great-grandson and only apprentice 'Mutantus' with his own followers started to refine and divulge it.
Especially sagas, whose players have problems with ArM5 p.159f Muto Vim and its layered errata (like in the discussion following this), can thus easily redefine the date of the publication of Triceres' results, and thereby make all of ArM5 MuVi but the Wizard's Communion and its derivatives (like TtA p.137 Day of Communion) either hard to access or completely unknown to most magi but the Mutantes.
Cheers