Turns out that you have to explicitly mount btrfs with the option compress=zstd (or compress=lzo as you prefer) to get any compression done, and I was not doing that. Also, to apply compression to existing data, you have to defragment with compression enabled. Alternatively, you can create a subvolume and set the compression property.
This explains it quite well.



Linux will run on a potato, and it doesn’t even have to have hardware memory management.