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I see a problem with this:
This is one of the most noticeable differences. With descriptor wallets, you cannot export the private key for one address. This is because a child private key combined with the parent public key can be used to compute the parent private key (and hence all other child private keys). This is a risk inherent in BIP 32's unhardened derivation. As such, descriptor wallets disallow the export of child private keys in order to mitigate the risk of accidentally exposing the parent private key.
But you shouldn't be exporting individual private keys anyways. The wallet does not use just one private key, so having an individual child private key is really not that useful.
If you want to export a private key that contains a reasonable amount to carry on a phone and import it into the phones Electrum wallet or whatever, then with the new format you wouldn't be able to do this, because apparently you will not be able to export individual private keys due the new format.
I get your point. But importing Bitcoin private keys to another device/wallet usually isn't recommended. Just create new wallet on your phone and send some Bitcoin to it.