Part of the reason that Result was kept out of the standard library so long is because it's duplicative of throws, which causes confusion. Result was also primarily motivated by asynchronous code patterns that we knew could be subsumed by an async analogue to throws in time. But we also knew that "in time" was going to be several years, and having numerous Result re-implementations in the ecosystem.
async/await may only have come up for formal review two weeks ago, but this approach to solving the problem has been around in the Swift community for ~4 years.
Doug