> looks sequential [but isn’t]

This is just wrong. It looks sequential and it is! What the original author means is that it looks synchronous but isn't. But of course that's not really true either, given the use of the await keyword, but that can be explained by the brief learning curve.

Swift concurrency may use coroutines as an implementation detail, but it doesn't expose most of the complexity of that model, or exposes it in different ways.

Sequential doesn’t mean reentrancy safe, something which has bitten me a few times in Swift concurrency.