So, I work for Redgate. Bias may play a factor here.
Static data masking may be OK in production environments where you have a degree of control. However, it won't work well, at all, in non-production environments where you have less, or no, control of the system. If someone is SA, they can bypass static data masking.
Most people don't use our tool (darn it). Instead, they have custom built scripts that clean the data and/or create data. This is a preferred approach. Permanently changing the data is far safer for non-production environments.