This is because of the “valid pixel expression” associated with the bands. Currently it does not use the GML masks (yet, in progress), but is set unconditonnally to “pixel value > 0”.
It happens that with B10, pixel value = 0 is valid… So we urgently need to handle all the masks properly.
You can edit the valid pixel expression from the band properties. Removing the expression, you will see black pixels everywhere, also in the no-data areas.