Could this be an attempt at contaminating the heirloom tomatoes by introducing a limiting gene in the pollen? It’s quite difficult to keep outdoor (home) gardens isolated from whatever other tomato strains are out there.
My brother accidentally developed a cherry-pear tomato cross that was magnificent, but we were unable to keep the seed line clean, and lost them. After over a dozen attempts at recovery, he has since died and I am at my wit’s end.
It may have been a random mutation...................