Let's be very careful with course names here. TPC Boston and Boston Golf Club are two completely seperate animals. TPC Boston is an Arnold Palmer that has been retouched by Brad Faxon, Gil Hanse, and a few other hands. Boston Golf Club is purely the Hanse team's creation.
Hanse's style is to let a good piece of land do the talking, at least I would say that is stongly presented at both Rustic Canyon and Boston Golf Club. Hanse's bunkers tend to be flashed up with shaggy tops and appear irregular in transitional natural areas. They tend towards a more formal curvalinear profile when surrounded by fairway. He is a master at employing natural land forms into the strategy on his holes. As an example, the 2nd hole at BGC employs a rock outcropping in the landing area that is in play for the longer hitter. I would bet that many architects would have dynamited that ledge. Hanse tends to set holes in wider corridors and employs strategy through width very well. You can often drive it away from trouble only to find the approach becomes more taxing by doing so. Hanses greens have significant movement to them, often in harmony with the surrounding land's contour. His greens at Rustic and Boston are wilder in contour than those at Applebrook, but that may be due to the greater topographical variations at the first two sites as opposed to the latter. It will be quite interesting to see how he contours the Olympic venue's greens, given that sites flatter character.
I don't know if that describes a style, or just tendency.
I would say that another architect who masterfully uses width, naturalness, shaggyness, contour variation, and angle highly effectively is Tom Doak, having just played Ballyneal. The virtue of firm soil is also a prominent feature at Holyoke.