Sure is, but in other hand, why not use "Unicode API" at first place.
I would guess they use Ansi API just as proxy to and from Unicode UTF16 API.
SomeWindowsApiA -> String Conversion to UTF16 -> SomeWindowsApiAW
Have not checked, just my hunch...
In other hand If they have UTF-8 enabled API that is not just proxy to Wide API, then it could provide speed improvement if App uses UTF-8 strings.