To a degree.
Throwing a thousand coders at a project of this small size would do no good, obviously. Having an extra coder to work on other segments in order to put the pieces together in the end when all you had before was a single coder doing all the heavy lifting? Totally helps out. People need to look at these things in perspective, not throw around generalized statements that can apply to anything.
What if the main coder (Dogeek) gets sick and ends up hospitalized for a month? "Well, tough luck then, nobody is around to do the work now and who is at the very least experienced enough to work the code without causing issues in the lon run. Guess we'll have to delay the project for at the very least a month more, if not more." - is basically what the current worst case scenario would be if that were the case.
Games like this are modular for a reason: You can totally have multiple coders work on different small pieces that all in the end need to fall in line. Coding guidelines exist and coders generally try to work so that their pieces all can be assembled and work in tandem. There is however the issue of having to work in a new member. He needs to get the grasp on how work is done in the new environment and what guidelines are to follow etc. That causes some slowdown at the start, but in the long run, having an extra coder is definitely gonna be an improvement.