Sure, the odds of a random mutation doing that are extremly low. I just added that because
localhost said that everything had a non-zero chance but this. And I'd say it's non-zero as well. Just very, very, very unlikely.
The other argument may be more likely though. Sure, genetics table get you quite far at least with most people, but if there are several genes involved with multiple variants, there might just be a few combinations of mother and father where this could happen.
And I certainly enjoy this more than accusing the devs. At least it is some nice conversation while waiting, don't you think?