Yes, it can export from descriptor wallets.

Not in a way that you would expect or would get useful results from.

The default mode of operation for descriptor wallets is to have a descriptor which contains a xprv from which the keys for the addresses in the wallet are derived. However, the derived keys are not stored in the wallet like they are for descriptor wallets. Instead, they are derived from the xprv when needed.

The xprv itself is not actually stored as an xprv. The actual private key component of the xprv is stored separately in the same format used for storing private keys that legacy wallets used. The xprv is essentially reconstructed at derivation time by taking the xpub in the descriptor and swapping out the pubkey for the privkey. So if you were to parse the records of descriptor wallet naively, you could create a WIF key that corresponds to the private key component of the xprv. But this WIF key would be absolutely useless to you as it is not directly used as the private key for any of your wallet's addresses, and it is not enough information to derive any of the actual private keys (you need the chaincode from the xpub to do derivation).

If your wallet has a descriptors for things that have the key directly in them rather than deriving keys, then yes, you would be able to get the WIF and have them be usable. But this really only happens if you import those things yourself, or if you migrated a pre-HD legacy wallet.

wallet-manipulator won't be exporting the keys for descriptors as WIF. It will instead reconstruct the descriptors with the full xprv so that users don't shoot themselves in the foot.