The Hynes, along with Back Bay Station, are examples of great "Big Ideas" that were fumbled in execution. Both of these buildings, by Kallmann, McKinnell and Wood, re-employ historical Italian urban design elements in contemporary form.
The thought, among architecture students at the time, was that McKinnell adapted thesis projects of his GSD interns, and just plugged them into the site. Back Bay Station, which takes the form of a basilica, brilliantly curves to reflect the track below, then drops the ball by denying the nave with a huge elephant cage enclosing the actual subway entrances.
Similarly, the Hynes uses the classic Italian shaded street arcade (think: Piazza San Marco, Bologna, Turin, etc.) but places it on the north side of the building. To add insult to irrelevance, there was nothing opening off of it. And as for the off-Gloucester Street entrance, there was some unconvincing song and dance at the time, but it seems obvious that it was, in reality, a miscalculation.
And I can remember being in the BAC student lounge, drinking and smoking (when such activities did not label you as "worse than Hitler") and laughing at McKinnell's explanation for that side wall. It was explained that the grid represented the memory of buildings formerly on the site. The joke? Before the original 1960's Hynes, there were no buildings on the site.