The anonymous_user_token field in the EditAttemptStep schema was added in T221195#5260013. The documentation doesn't reflect that the field is only set for IP editors that are part of the VE mobile default test, per T225209, and therefore might confuse the reader to believe that this field can be used to reliably distinguish between IP editors. That's not the case as the field largely contains NULL-values.
Solution: submit a patch that updates the description of the field in the schema.