Wouldn't it have been a much better choice to use hardened derivation?
Hardened does not allow for child pubkeys to be derived from the parent xpub.
I can think of something: I once needed to (quickly) use CPFP, but Bitcoin Core's GUI didn't allow me to use an unconfirmed input from a third party, so I exported the private key and imported it into Electrum.
That's a workaround, not a use case. You could still do this workaround by exporting the descriptor with private keys.
You can use the RPCs to make such a transaction since you can manually specify the inputs.
Importing a private key is so much easier in a non-descriptor wallet.
It's pretty easy with a descriptor wallet, you make a
combo(<privkey>) descriptor and import that. With descriptor wallets, it's also possible to import more complicated things like anything involving an xpub, and you'll be importing exactly what the descriptor describes instead of also things that you don't expect when you try to do something similar with a legacy wallet.