Problem: Out-of-memory for many snapshot deletions -> Feature Request: use "btrfs subvolume sync"

I am using an ssh-based backup of many subvolumes to a remote arm-based NAS device.
This device was offline for a long time.
Now when running the usual btrbk routine, the device kernel gets out of memory-errors during the subvolume/snapshot deletion phase in btrbk.

I **assume** this is due to the fact that the btrfs subvolume delete command instantly returns, and btrbk just issues the next one.

--> Would it be possible to add the "btrfs subvolume sync" command in between subvolume deletions? This would make sure that the current delete operation(s) are finished before issuing the next operations - and thus hopefully avoid the OOM.

Thank you very much in advance!