Certainly agree on this point, but also don’t want to leave wallet users with the impression that this is chosen as a standard because revealing that only the script path was usable is always bad for privacy.
Good to know! For BIP352, the scenario I had in mind for revealing that the keypath was unusable is a coinjoin, where Alice wants to coinjoin her provably unspendable keypath UTXO and Bob wants to make a payment to a SP address. It sounds like in this scenario Alice could provide a signature for P - H to a coordinator, instead of the coordinator requiring that her script path spend show that H was the internal key.
EDIT: nevermind, this doesn’t work. It’s about the receiver knowing that the taproot spend was a script-only spend, and AFAICT there is no way to do this in a non-interactive way outside of making it public that only the script path was usable.