In the industry txid is known as "transaction hash". Why wasn't the "hash" field called "wtxid"?
1 Answer
The idea is that it is returning the hash of the entire transaction data. Currently, that is always identical to the wtxid.
But in a hypothetical future, where more data may get added to transaction serializations, in addition to the base data (covered by txid) and witness data, hash would change to always cover everything.