Some observations from playing around with the planner:
If you're headed eastbound from Bayview it will tell you to board a westbound train and then stay on that train since it will be doing a return trip immediately afterwards.
This might suggest that only one of the platforms at Tunney's will be used initially (and tbh that makes perfect sense).
This was another suggestion for the same trip... uhhh. Only ~10 minutes longer though! (90 is the current 87 right?)