The street view of the alley shows what I saw first-hand this morning: it's a wide, clean alley. Nice enough as alleys go.
But bikes don't go in alleys. They go on roads.
I submitted a problem report under the "Directions suggest a route that is difficult or restricted" category, because there wasn't an explicit "Directions suggest a route that is unsafe" category.
Bicycles should not be directed through alleys. It is safer for the cyclist, fir [sic] pedestrians on the sidewalks, and for motorists on the streets if the cyclist behaves as much like a car as possible. They should stay on the streets, proper.
You wouldn't randomly or spontaneously drive your car through the alley for several blocks. It wouldn't be safe!
And if you wouldn't drive that way in your car, you shouldn't drive that way on your bike.