As a millenial programmer, I think you're spot on. The previous gen and some of the older millenials still remember the old internet of chat rooms, forums, IRC, etc. Lemmy and Reddit are very similar. It's familiar and nostalgic and I think ends up drawing more of the older crowd. Older non-programmers are stereotypically not really tech savvy enough or don't have that old nostalgia driving them to use Lemmy. That may be why you see this behavior more from that community.