Another data point: I get those to an email that was exclusively used on one insecure message board, but not only with the actual password that I had been using

Another data point: I get those to an email that was exclusively used on one insecure message board, but not only with the actual password that I had been using there, but also with a number of comically mangled variations thereof, and with some completely unrelated passwords (not mine). Apparently the data has been compiled from many different sources that went through various stages of bitrot from changing hands repeatedly, possibly with deliberate cutting to inflate numbers. (oh, and also myspace, some identities are just meant to be stolen I guess...)