Since MMPO returns ties relatively often, a tiebreaker is needed. FPP is the most obvious one, and also doesn't differ much from other tiebreakers. The comma notation in "MMPO,FPP" signifies that one doesn't eliminate the MMPO non-winning candidates before counting first preferences.
49 A 27 B>C 24 C 100
MMPO,FPP breaks the MMPO tie between B and C by electing B, who is not allowed to win according to Plurality.
It can easily be shown that electing C instead would result in a Later-no-harm violation, because if the C voters add preferences for B:
49 A 27 B>C 24 C>B 100
It's not possible for a sensible method to elect C anymore.