Using loopdev for zRAM writeback feature

Documentation states that zRAM writeback feature supports only swap partitions as it's backing_dev. But I've successfully used a swap file too, by attaching it to a loop device

losetup /dev/loop0 /swapfile
cd /sys/block/zram0
echo /dev/loop0 > backing_dev
echo 8G > disksize
mkswap /dev/zram0
swapon /dev/zram0

After this, swapon -s shows zRAM device enabled, cat /sys/block/zram0/backing_dev returns /dev/loop0 and echo huge > /sys/block/zram0/writeback works with no problem, with cat /sys/block/zram0/bd_stats confirming that the write indeed succeeded Can this be used, or does this method have some kind of nasty drawbacks?