No, of course not. Back then, Leo probably went to the same surplus shop as I did, and found a nice roll of #42 wire. It was cheap, because nobody used that size for anything, you know, useful. He took it back to the shop, messed around with it, and worked out a recipe for a pickup that sounded good with his funny new guitar. He set up the production line to build that recipe of pickups by the millions, and they still build them about the same way today. It's a known recipe that works for that guitar.
The silly old wives tale part is believing that because Leo and Fender use #42 wire, therefore you must use #42 wire to make any pickup sound good. That the #42 wire is the magic ingredient that makes that beautiful sound. That's stupid, and I'm sure that Leo would agree. He could have used another wire size, and a little different recipe, and arrived at the same product. My guess is that he chose that size for practical reasons of mass production. He was trying to minimize the pounds of copper per pickup, to keep the cost low, while not making the wire too fragile to work with on the assembly line. #42 was a good compromise. So he made it work. Leo was an engineer.
