Clearly, SFOS not only utilizes drivers / firmware from AOSP binaries but also from the underlying Android OS.
Android (e.g. when flashed via Emma) creates an AWFUL LOT of partitions, of which SFOS then replaces / reflashes only a few, whereas the whole rest remains intact, including things like baseband, dsp firmware, Bluetooth, etc.
Also, I’ve seen several times on this forum how Jolla people were saying that drivers from the underlying Android are still used by SFOS, see e.g. this post by @flypig, where when asked whether SFOS is using the installed android or completely replacing it he replies that “there are elements of Android (drivers) that are still used by Sailfish OS”.
Anyway, it is very easy to verify it yourself. While using in both cases the exact same AOSP binaries, first flash SFOS over Android 11 and note how display functionality is flawed with awful tint and banding, plus the echo issue is also there. Then flash SFOS on top of Android 13 and see how those issues are simply gone. As in both cases you’re using the same AOSP binaries and the only thing that changes is the underlying Android version, it is the best proof that it is drivers from the underlying Android what affects that specific functionality in SFOS.