Oh, that's interesting. So in the TPM case, I could not have a password to have an encrypted volume? And if I removed that hard drive from the computer, there would be no way to recover it? But from the user's perspective, it would be transparent and they might not even know it's encrypted?
Yes, that's very common. In Windows 11 Pro (not sure about other editions) you can enable BitLocker and turn on auto unlock with no PIN. Though if someone steals the whole PC I'm not sure how effective that is. With a PIN set the TPM will enforce rate limiting to prevent brute force attacks, which should be more effective in that scenario. Most modern phones do something similar: user data is encrypted with a TPM key accessed using your lock screen code on boot-up.
