Yes, that does look like a bug. I'm guessing what happened is it's a binary, but they're inserted as separate stars in the catalogue, and because their location is almost the same the procedural generation makes very similar systems for them. I've had the same thing happen with Alpha Centauri once while I was messing about trying to get rid of the Avatar planets and get procedural ones instead.

So my guess is the brown dwarfs aren't real, but got added by the procedural generation.