Please ELI5. What I have learned is that the added passphrase, or the "25th seed word", is a feature all BIP-39 compliant wallets have that generates a new set of keys. It's doesn't matter if the user owns/uses a Trezor, a Ledger, or any kind of hardware or software wallet. If the user enters his 24 seeds + his passphrase, the output will always be his/her "hidden wallet". Are you saying it's not?
No, I wasn't saying you won't be able to recover your hidden wallet in some other wallet software. I am saying Ledger tries to make passphrases less secure and more user-friendly, which, together with the announced Recovery service, is going to make a hardware wallet no better than a regular hot wallet. Passphrases should be kept separately both from the seed phrase and a hardware wallet itself: that's a rule that should be followed regardless of proficiency in security matters. Ledger relies too much on encryption and third parties not breaking trust and not sharing user data with unwanted entities, but we all know that the former will not protect if the decryption key is revealed, and the latter just goes against Bitcoin principles themselves.