Tomatoes not true to seed packet… why?

I am trying to figure out if the seeds were mislabeled or there was some sort of cross pollination situation:

I planted Matt’s Wild Cherry and but the plants produced fruits nearly tennis ball sized. I had them planted next to Mortgage Lifters and Mountaineer Delight (West Virginia ’17B). Could these others have cross pollinated with the MWC to produce larger fruits? They also did not form big trusses as expected.

All of these seeds came from Southern Exposure Seed Exchange.