Thanks for pointing this out! It was indeed incorrectly documented, but matches probably some need.
It will have been added in the next BETA release as new functionality. The next BETA should hit the market typically within one week.
Please note that the current SQL engine has a tucked away advanced sister. The next Invantive SQL engine will improve especially in scalability and optimization techniques. Various static generation techniques from SQL to executable code such as in Invantive PSQL will be replaced by more dynamic generation techniques that enable more advanced optimizations.
For most companies that will not be a concern, so we are developing it in parallel to the current SQL engine. The date mask has been added to both engines. The changes in the next generation SQL engine are especially relevant when you process very large amounts of data in parallel using PSQL or many queries.