It can be either TCP or UDP. Regardless, UDP has a checksum as well.

The likelihood of a bit-flip is very uncommon. Even taking into account the volume of computers out there, the likelihood of a bit-flip at the exact spot (in the domain name) and moment of a DNS lookup (before the checksum is calculated) is astronomically uncommon. This article is garbage.

I wonder if there are more sources of error than just RAM bit-flipping. The bit could be flipped anywhere it's stored or passing through. If that is the case, the error rate would be orders of magnitude higher.