Hopefully not in this particular example, because it's an observable change in semantics as you demonstrated by printing the type. Perhaps it could be done in situations where the difference isn't observable, though.
To be fair, Swift could (does) have optimizations that essentially do the equivalent of what is being suggested, by way of stack-allocating the array buffer and eliminating some of Array's abstractions. But as @jawbroken points out, it can only do this in (mostly) non-user-observable ways so it would never change what's happening at the level of the type system. It also needs full visibility of the code inside printTypeOfSequence to make sure e.g. the array doesn't escape.