While most of the functionality of Sailfish is good, the car handsfree support is atrocious. The car handsfree support has been nothing but bad from the beginning of Sailfish. Previously there were problems with Bluetooth disconnecting all the time because of power save disconnects BT. This has now been fixed somewhat but still it sometimes disconnects.
However, one problem is that sounds quality is unusable. The muffled sound forces me to hang up all the time. Then when I use an old phone (a Nokia, today 10 years old) that supports all kinds of things including rSAP, the audio quality is excellent. I cannot say what type of BT connection it is using though. I have tested this with several cars and it was similar bad audio quality on all them compared to other phones with better support. Network signalling quality has nothing to do with it.
Since the audio quality has been notoriously bad, why not let the car handle it. rSAP would solve this issue as it is the car that is handling the audio now.