Yes, there are other ways of doing it as well, you can plug in a live iso and chroot into your proper root and change it for example. This is why you can put a password on GRUB and on your BIOS, even if both of them have passwords, someone can remove your disk plug it into another machine and access your data. Long story short if someone has physical access to your machine is essentially game over. And BTW this is also true for Windows, physical access to the machine has always been considered game over because the person can simply remove the disk and plug it in another system, so any software solution is useless.

This is why encryption is important, if your disk is encrypted putting it in another machine gives garbage unless you know the encryption key, making root rw (as in the link) is useless because you still need to decrypt the disk to access it, plugging a live iso is pointless because unless you know the encryption key you won't be able to chroot into the system. But for most people the fact that no one untrustworthy will ever be physically near your computer is enough to not warrant extra measures of security, not to mention that most people don't have data that could be problematic if leaked (e.g. source code for a large company) and those who do have their drives fully encrypted.