Using verify query on light clients would require them to be supplied with the expected root hash, in addition to the proof, keys and signature. Since the proof already contains the root_hash, and any other root hash wouldn't match for the signature, it would be optimal not to send it.
The change requested adds a new function that executes the proof and returns the root hash and the elements. That root hash can then be verified by a signature scheme.
Using verify query on light clients would require them to be supplied with the expected root hash, in addition to the proof, keys and signature. Since the proof already contains the root_hash, and any other root hash wouldn't match for the signature, it would be optimal not to send it.
The change requested adds a new function that executes the proof and returns the root hash and the elements. That root hash can then be verified by a signature scheme.