Or is there more to it than this writer is declaring?
uses the EXT4 filesystem by default. You can convert the filesystem to BTRFS to take advantage of the in-built compression features. Using compression can reduce the disk usage by up to 60% without any noticeable impact on CPU usage. It also improves storage performance, since less data needs to be read and written to the SD Card. BTRFS also supports filesystem snapshots that allow you to roll back the system to a previous state in case of issues.
The article is about Ubuntu on raspberry pi, but may relate to debian in general.
I'd really like a pointer to a non-technical how to set it all up, if accurate