Concurrent processing allows you to have the advantage of having an earlier 485 receipt date. You don't have to wait for the 140 approval to file ur 485. This obviously has benefits when it comes to FIFO processing (note: I am not implying that BCIS necessarily follows it in practice) and more importantly, using AC21 to change your job. You now don't have to wait the extra time that would be required for 140 approval.
However, to answer your question, concurrent processing by itself does not change anything in the process to make it go faster.