To me, then Beane should have cut him much sooner so McKenzie could find another team or at the beginning of the FA period.
What sense does it make to wait so long to cut McKenzie after all the WR FA positions have already been filled ?
Harty is most likely a replacement for Crowder not McKenzie.
I expect Dorsey to keep the slot platoon of McKenzie and now Harty instead of Crowder.
Also you can't have Harty playing full time because of his small size and is prone to injury.
So you want to limit his snaps to keep him healthy.