The "extension" here (the _s functions) is standardized; while in the EEE strategy the extensions cannot be standardized: the whole point of the "extension" phase in EEE is to prevent interoperability.
Except that the microsoft versions of the functions are incompatible with the standardized versions.
(I don't think that that was done in bad faith, however; only that wg14 decided to change the definitions from the microsoft-proposed ones, and microsoft didn't feel willing to break compatibility.)
