It is not necessary but still better to run both online discard and batched fstrim. from man:
Also, a device may ignore the TRIM command if the range is too small, so running a batch discard has a greater probability of actually discarding the blocks.
Doesn’t btrfs do this already?
Yeah, it’s unnecessary with btrfs on somewhat recent kernels since it now enables discard=async by default.
It is not necessary but still better to run both online discard and batched fstrim. from man: