You're right, but the reason to do this isn't connections. Logan has already had some real problems dealing with consolidation of airlines, perhaps climaxing in the fact that United will have operations in 2 different terminals for the next several years. The cap on B is to accommodate United and US Airways in a single Star Alliance space and increase flexibility, but all the chips have not yet fallen when it comes to mergers. What happens, for instance, if JetBlue and American, who have become increasingly close, want to colocate?
Logan really ought to have concourses with new gate areas that connect B-C and A-B, as well as the planned C-E. That way, airlines could be flexibly accommodated however their needs change. The 5 (now 4) airline-specific terminal setup has been anachronistic since the end of regulation.