It's fairly common to find those Y type brown dwarfs around those high mass stars and rings aren't too out of the ordinary for them either. From my understanding those things are closer to gas giants than stars anyways. Finding another type of star with rings would be pretty rare though. I think the thing you overlooked that is probably more rare than those stars is the little ringed landable planet (HMC or Metal-rich?). There was a statistic posted in another thread about ringed landable planets and I think it was somewhere around 2% of landables have rings. Not sure on the likely hood of finding those ringed Y-types but in my experience it's fairly common (I'm sure someone will post the stats if you ask nicely). Still a neat systems though and if it's something new to you then all the better!
o7 Commander