I keep getting emails from various vendors saying that the MPX was redesigned for 2019. There was already a Gen II, what does this new redesign encompass? From the pics I see in those same emails, the only differences I notice are an MLOK handguard and new flip up irons. Did they make internal changes as well?

I don’t know that this is necessarily a generational change. It looks like they’ve put the Timney that they already used in the PCC.