I think most people tend to not read the about section. I used to have mine super long, a lot of detail about what I do, what I offer, etc. but it was obvious that the people jumping on were either already going to support me regardless, or ended up leaving out of confusion for what rewards I offered. (Which was explained in detail in the about that they obviously did not read. Patreon’s navigation does not help either.)
My fix: shorten up my about section as much as possible, make things super clear and to the point, and take the information that’s more geared towards supporters (such as more info on rewards) into the welcome message. The rest is bare bones just the basic stuff that someone new who is not familiar with me might need to know.
As far as if it helps get people to join, I’d say perhaps somewhat? (My experience is limited.) But I’d say what does the most is just having those hardcore fans turn into supporters. Building up your base elsewhere is what leads to growing your patronage, since those people will just want to support you regardless of what you offer. Plus the more you grow your base, the more non-hardcore fans might be curious about what you do and will check you out too. I feel like that’s more the target audience for the about section.