A 5th guy / gal could accelerate the release by a lot.
Not really. I'll point out my involvement with Raptor here and remind you that the game was still delayed due to other things at the time. Adding me helped relieve some of the bottleneck but there was still a bottleneck.
As I know nothing of your involvement, capabilities, role on the project or anything, then no clue why this particular situation didn't help, nor why you're pointing to it. From what I've read and seen you do (SBR and AI war 2), we have very different values when stuff needs to be done. Not that it matters.
However, what I said came from 10 years of working in development in different roles... and yes, adding someone else to reduce workload, and time, works. However, I'll agree that not always : there are conditions for it to work.
In my experience, main points are that the right profile has to be found (the newbie must be able to take over, or liberate, someone working on the bottleneck), workload prevision need to be are adequately defined, scope must not change from start to finish, or only "minor-ly" (a point on which video gaming as a whole has issues) and whatever project you're working on needs to be cut and cuttable into independant pieces, so work can be divided properly, and small size of team. More people mean more communication channels and lost time - again "cutting" scopes into independant pieces must be done.
Hence why I said "A 5th guy / gal
could". Because sometimes, that's the solution. Other times, it's a waste of time.