That would be for the standard wallets, but what about the multisigs? is there any cosigner index implied? that post didn't point that out.
The derivation path is the same for multisig addresses. If you want to check for yourself then restore a wallet with the following xprivs:
a: xprv9s21ZrQH143K2j4ApvAWXbXnRQxxY1175NJFyzRSL3copkzRrmR9iFju2bPKMThZZ5X8dBHY8Hn
So3Tp1mosezGpbhMxjFewR7fWsWqVuzd
b: xprv9s21ZrQH143K2dEFaB8GQ9FmTdLyMijhPngdimqyUiwXgh5rmh92n4x6JEWutHeDi2qAAHPv92S
3SuhNuktYZt22p2jgWMoK5WkDXBnkj4S
The above two are generated using bip32.org (passphrase a and b resp.)
The first address pubkeys of the above two are (m/0/0):
a0: 0223bb76b4e6844a6bde363057fab2aa5df5bc3a7e89c7e8124f6265f8080065fa
b0: 0246277670f2d0ff5e86af5e82f8f98d3e1cd90d0b0f252df6518fd842568a5551
And the resulting address is 3Nw1BqfMgdLDAsu67g74dJLxSPAxQEmfZz. This is what you will see in electrum as well as on coinbin:
https://coinb.in/#newMultiSig