They also don’t say it doesn’t.
Here is an an example of streaming to two Airplay 2 devices one a Wiim Pro Plus from Qobuz app on my iPhone.
You can see them grouped in the app which you can
only do via Airplay2.
Here is what my iPhone is sending out at this point in time. 1.5mb/s which equates to 2x lossless ALAC streams at 44.1/16.
Here is what Wiim app says although this metadata is easily given wrongly and Wiim have for here. It tallies up with the data rates from my phone. Phone wasn’t doing anything else other than Airplay.
If this isn’t proof enough then you can believe what you want to, the whole implementation in each app is what decides how and what it streams.