This was my experience exactly. Aside from helping me pick up a few concepts more quickly than I would have otherwise, I did it purely to get my foot in the door for interviews. It also was a good excuse to just focus on my portfolio for several weeks whereas if I had held a full-time job during this time, it would have easily taken me 4x as long.

It's a super expensive and wasteful way to do this, but I was optimizing for my time.