[I think the loop has been officially changed. The buses now drop off their passengers on Broadway etween 107th and 106th. After the layover, they u-turn and pick up passengers across Broadway.]
Yes, some or most M60 drivers do that, and they are off-route. The sidewalks on the Broadway side of Strauss Park (from 107th to 106th) are cobblestones for the first four feet or so from the curb; cobblestones are not an ADA-compliant surface - wheelchairs can't navigate over them - so a bus stop there would be illegal. Since that park was renovated only a few years ago (I was active in the local Block Association at the time, and involved in the process), it's not likely to be redone for a long while, so the cobblestones are staying put.
I was back up there on Sunday, April 8th. The stop on 106th, near side of Broadway, is still signed for M60 to the Upper West Side, and the M116 still picks up on 106th at the far side of Broadway. (Again, it was moved out of the near side stop to make room for M60 layovers.
BTW, the only NYCT routes SCHEDULED to make U-turns on Broadway are the Bx19 at 147th Street (when Riverbank State Park is closed) and the Bx9 at 262nd Street. (Before anyone starts screaming: No, the M104 short-turns at 106th are NOT scheduled.)