From the article:

> The OS may stop you from unmounting /dev/sda1, but it won’t stop you from writing to /dev/sda1 or /dev/sda even if there’s something mounted!

Not always true. There's a kernel config option that allows it. CONFIG_BLK_DEV_WRITE_MOUNTED

It's worth noting, though, that that config option was only introduced in kernel version 6.8! Before then the option didn't exist and you could write with impunity to mounted devices (as root, obviously).