I just read the mac page about SSD encryption by the T2 chip here
Always back up your content to a secure external drive or other secure backup location so that you can restore it, if necessary. You should also turn on FileVault for additional security, because without FileVault enabled, your encrypted SSDs automatically mount and decrypt when connected to your Mac.
I am confused. Isn’t encryption only useful when it does not automatically decrypt? This seems rather useless. I guess it prevents certain kinds of attacks: someone steals the SSD from the device using advanced techniques without stealing the whole laptop. In this case, doesn’t it just make sense to take the whole laptop?
What is the purpose of the encryption provided by the T2 chip? I know the benefits of FileVault 2 though, which also makes use of the T2 chip. However, to decrypt this FileVault you need your user password. To decrypt the initial T2 encryption, you need nothing?