I don't think that all the fuss is about ASIO it self.
My guess is that the special ASIO Driver chosen for Windows is only serving as a means to an end. In other words, to activate this alternate setting provided by XMOS.
Since is is stated that this feature "Will be generally available with the next ALSA release (1.0.29)" it makes no sense to talk about ASIO and its special Windows driver.
https://github.com/lintweaker/xmos-native-dsd states clearly that with that alternate setting provided by ALSA release (1.0.29) the things are are working out.