etrex 30 tracking II - differential on GLONASS

Took a walk at lunch time and went to a place with a clear sky view.

Mode: GPS+WAAS+GLONASS

Quickly, satellite number 46 appeared (as well as GPS, GLONASS sats).
This corresponds to WAAS sat 133.

Then, a couple minutes later, the 6 GLONASS sats I was tracking went to
"D" mode (differential).

I'm pretty sure WAAS is not broadcasting differential for GLONASS. So I
wonder if the unit was also tracking 120 or 122 (EGNOS) but not
displaying it.

(Unlike Saturday where I was sure I saw "33" on the display (120)).

It would be nice if Garmin were more clear about what is going on in
there...

--
"I see!" said the blind man as he picked up his hammer and saw.