Please do test it. If you need help keeping counts, I’ll be happy to set up a spreadsheet for you. If you upload screenshots, I’ll also be happy to help you count tiles.
But you have to upload/count every board, not just the bad ones.
If you’re not actually willing to test your theory, though…well, that will say a lot too.
After diligently recording over 580 raids, though, I can tell you that I haven’t seen any evidence of a bias. And I’ve uploaded the data to the forum, so you’re welcome to look through it and point out where I’m wrong.