Probably so. Though I would suggest that the neither one is a small niche in itself. Mac especially--it's the favored platform for every developer I know except one. Yes, it's less popular outside tech circles (probably due in part to the price).
Imagine this scenario: There are tons of Mac users who want to learn Haskell. They try it, but can't install libraries. The Haskell community never hears from them; one could say the system failed silently. Meanwhile, Linux works fine, and the Haskell-Linux community keeps growing.
So perhaps there's a self-reinforcing Linux-centric bias in the developer population.
Your general point - that it's likely self-reinforcing - is certainly strong. I'd even expect it to be exacerbated a bit in this case by it being GUI things in particular showing issues, where (at the risk of stereotyping) there is probably a correlation between those who prefer a Mac and those who prefer a GUI.
Interesting. It must be clustered, as you say.
I use a Mac largely because there are a handful of professional apps that don't run on Linux. (Otherwise, I'd probably go with Mac hardware and a Linux OS.) Which implies that the demands of my industry is what pushed me (and perhaps the people I know) onto Macs.
> there is probably a correlation between those who prefer a Mac and those who prefer a GUI.
It's not so much that I personally prefer a GUI. (I don't, in general.) It's that I make a lot of software for other people, so GUIs aren't a matter of preference but of professional obligation. Also, there are certain applications I'd like to do where a GUI is pretty much the only sensible option: Design tools, certain types of games, etc.