As a general rule, I expect a file on an encrypted disk to be encrypted with a key derived from a password I provide.

I think it's time to update your expectations. Hardware security modules have been around for quite a while. You shouldn't assume that your chosen password is the only input to the key derivation, or even that the raw key itself will always be obtainable.

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shaky-carrousel 42 minutes ago | parent [-]

I never assumed that my chosen password was the only input to the key derivation. Just that my chosen password is at least one of the inputs to the key derivation. LUKS has been around for quite a while.

	▲	wtallis 31 minutes ago \| parent [-]
		You're asking for the encryption key to be derivable by an unrelated system that only has the encrypted file and your password.