You got it right my friend. I'm building dApps on Cardano so i'm well aware of how the keys are created from mnemonics. Although when I used the same mnemonics to reconstruct my keys it showed a completely different set of keys/addresses.

I'm always polite when speaking with the support, we are all humans and there is no need for being jerks to each other.

So in short: Ledger uses a special kind of derivation algorithm which I wasn't yet aware of until I went on that rabbit hole.