[Question]: WriteBatch and Transaction method return types

I'm working on an internal code library and I have some code that is only concerned with `set()`, `update()` and `delete()` methods of `WriteBatch` and `Transaction`. I notice the only thing that differs between the methods is the return type. Transaction return type is `:this` and WriteBatch is `:WriteBatch`

For example the set()'s:
- https://github.com/firebase/firebase-js-sdk/blob/master/packages/firestore/src/lite-api/transaction.ts#L130
- https://github.com/firebase/firebase-js-sdk/blob/master/packages/firestore/src/lite-api/write_batch.ts#L76

I wondered if it would be a possibility for them to all use the `:this` return type? I'd like to be able to use the 2 types interchangeably based on an interface of only those few methods. Thank you for your time.