attachments w/ isAudioMessage:true not playable on iOS

[d4tocchini]

When I send an attachment & set isAudioMessage true, the message works correctly on recipient's MacOS Messages.app:

But, the same message on iOS shows up like below and is not clickable or playable:

To make it playable I have to turn off the isAudioMessage option. This makes the audio showup the same as above but at least its playable on iOS.

The audio buffer is an mp3 and whether I use isAudioMessage or not, it seems to always convert to caf. Is this expected?