What with the focus on the not-to-be direct access from 128, a potentially important improvement to the Riverside story has been overlooked. In the previous incarnation, cars exiting from the west side (along the 128 ramp) could only go right. The developer has added a two-way approach to this entrance from Grove St., so cars can exit the development without going through the entrance directly on Grove St.
Turning towards the development's (back entrance) from Grove St., traffic would have two choices: to the development or to the 128N entrance ramp. From the development, traffic would have two choices: left to Grove St. or right to the 128N entrance ramp. The plans call for a flyover for the ramp-bound traffic from Grove Street over the development entrance.
Creating an exit out of the back side of the development will relieve pressure on the site and on Grove St. Traffic from the office buildings on the west end of the development won't have to go through the development and out Grove St. But, the flyover precludes an opportunity to make the stretch from Grove St. to the back entrance a local road, complete with on-street parking. There's no reason that traffic to the on-ramp can't negotiate a mini-roundabout or traffic signal in front of the back entrance.