The immediate answer to your question is no, from what I've been able to find there's nothing that would make Aberdeen special in the formation of Melvins or Nirvana.

However, by merit of Aberdeen being such a small and (relatively) isolated town, the paths of Buzz Osborne, Dale Crover and Matt Lukin, and Kurt Cobain and Krist Novoselic, was inevitable. It's a (fortunate) coincidence that the initial members of Melvins were rehearsing and then playing shows in and around Aberdeen, while Cobain and Novoselic were in High School and within the age demographic of kids who would be going to their shows, and were enthusiastic about making music. Furthermore, it's very clear within Nirvana's early work that they were heavily influenced by Melvin's slow, sludgy, heavy guitar lines, with rumbling vocals. You can hear this yourself when you listen to what Cobain and Novoselic would have listened to when they would have hung around the studio they shared with Melvins, or went to one of their shows, and then compare it to their more sludgy-sounding tracks from Bleach.

So if you follow my line of argument here, you could say that: because one of the few active "rock" bands in and around Aberdeen happened to be Melvins, who pioneered the genres of Sludge and Doom Metal that Nirvana began playing and later developed into Grunge, and also happened to share common influences with each other (Cobain and Buzzo have both stated Black Flag's Greg Ginn as being very influential), the fact that Nirvana's most direct, tangible influence was there by merit of Aberdeen being a small, isolated logging town, was crucial for the sonic founding and development of Nirvana, and probably grunge at large. Dale Crover even filled in on drums for the demo tape that would later be developed by Cobain and Novoselic into their debut album, Bleach.