I have noticed the same thing. I am finding seedlings of G.macrorrhizum, lots of G. pratense and, much to my surprise,
G.'Brookside'. I can't wait to see how these come out.Then there is G. pyrenaicum which almost behaving like a weed this spring.
Leo

I thought I had lost all my G. pyrenaicum a few years ago.But this spring there are several new ones starting. Perhaps the seeds had laid dormant in the ground and all the rain we had in May brought them to life.
Tons of phaeum & maculata, quite a few Max Frei and even a Shepherd's warning.

No, can't say I've noticed a difference here, all my hardy geraniums seem to produce seedlings each year in approximately the same numbers....EXCEPT nodosum Svelte Lilac. The description reads self sows politely....it could be rude if it (they, there are two) wanted; I was hoping for seedlings and have never found any at all. Not even doing hands and knees searches; plants have been in the ground and blooming about 4 years.