I bought this book 'Wildhorn/Wildstrubel blüemlisalp from Ueli Mosimann (SAC)(2011)
He states that the Morgenhorn from NorthWest is ZS (Ziemlich Schwierig = AD). But when I browse Summitpost:
https://www.summitpost.org/bl-emlisalp-group/150804
I see PD.

Same for Wyssi frau and Blüemlisalphorn.

Which is the correct grade? Why is there such a difference in those gradings?

Are there alot of dangerous crevasses in the morgenhorn glacier?