What would be the point of them saying it only works with Acolyte if it doesn't? Given that they make 8 speed Shimano compatible shifters as well you would think they would say if it was cross compatible so they could make more money. If I already have some bottom end Shimnao stuff (or really old stuff of quality from the late 80s or early 90s) and I needed a new derailleur I would think MS would want to capitalize on that by having cross compatibility mentioned if it was the case. However in this case it is a dedicated groupset to be a sort of higher quality alternative to the crap that usually exists in that space mainly for kids bikes because those get neglected and relegated to Tourney level garbage that kids have a hard time shifting because nobody thought a stiff poorly made twist shift was a poor choice for little young hands.