FWIW, I think it's the right choice that all you have to do to write a test is write a regular Swift function and add @Test to it. That's clean, simple, and the kind of progressive disclosure Swift is based around.
As much as I would like to have the ability to give cleaner/more descriptive names to tests, I don't think having tests be written a bespoke different dialect of Swift would be the right direction. The framework has to give that thing it creates some name, and while test outcome reports can use the descriptive name, the minute you look at a stack trace or a debugger you're in an environment where the name of that function is visible but not obvious from source because you didn't write it.