Well not quite... Frank correct me if I'm wrong... Nirvana DOES have a good rep; not stellar seeds but solid, they're just cheap, and the F2s almost by definition have increased phenotypic variability, which can actually be a POSITIVE thing if you buy a pack of seeds, grow them all out, and keep the best for a mother, because while with all the differences you could hav a couple crappy ones, a few average ones, and an exceptional female worthy of cloning the living fuck out of.
Even though they are F2s they ARE the same strain, but not exactly as the original breeder had intended necessarily, unless that strain is stable to begin with. Here's the funky part, if the strain was originally an F1 hybrid (common), for the F2s to be more similar, the ORIGINAL parents had to be fairly similar! Anyway yeah, go read up on your Punnett squares and Mendel's peas, lol.