Originally Posted by
anteater
No, the underlying ticket basis does not change. Since March 2021 (IIRC), award tickets book into the same underlying fare classes as revenue tickets rather than separate fare classes.
Meaning, an award ticket who uses this feature will still not earn miles.
If the underlying ticket doesn't change, how do revenue tickets get the bonus but not awards? The upgrade also books into an award fare class? Either way it doesn't specify an exclusion to award tickets...
Edit: I guess there's a catch-all semi-hidden on the mileage earning chart page about awards not being eligible in general (not upgrade specific). Still if you are paying cash for the upgrade they should really clarify that, if it's true you don't earn miles.