To give you the short version, the developer & city made a concession under last minute pressure from West End/North End nimby's.
The BPDA then turned around and leveraged the "give" to approve the Garden Garage/Alcott after the concession of just a few floors and garage spaces.
*Nimby's recoiled in horror City govt would have the gall to approve in a 5-0 vote, a 44 story residential tower, scrunched into a cluster of other urban, residential highrises, in the heart of a medium/large American city.