You're hitting a pet peeve of mine, which is the "all or nothing" misunderstanding of security. You should evaluate security against a threat model.

Those assumptions that you criticize hold true for the realistic threat faced by the vast vast majority of people: opportunistic taking of personal data by device thieves, intruders, and others with physical access to the machine. If you are worried about more sophisticated attacks, then you can easily ratchet up BitLocker's security by requiring a boot-time PIN, dongle, or password in addition to the TPM/SecureBoot measurements. You will also want to be more selective about the hardware that you use.

I meant only that the default behavior makes a non-trivial set of assumptions about the higher-level layers. Of course there are trade-offs, especially between usability/user expectations and security. Honestly I was just trying to shoe-horn a fun quote into the conversation. ;)