Yes we have to deal with throttling now on /admin/api/unstable/graphql.json, but that's a whole separate topic for another thread.
Noteworthy for this topic though is that this still only works on the unstable branch. Their have been several updates to the API since this was originally posted but the latest https://shopify.dev/docs/admin-api/graphql/reference/object/ordertransaction?api%5Bversion%5D=2021-0... still has the critical "receipt" field missing.
The unstable branch continues to work, although it still has that bizarre double-encoded JSON.
Huh I just looked at https://shopify.dev/docs/admin-api/graphql/reference/orders/ordertransaction?api%5Bversion%5D=2021-0... to see if it changed. "receipt" is still deprecated. However they added a new field called "fees", which may finally have the actual core information of "ordertransaction" in a normal format? Haven't tested it though.