you sort of want someone who sucks at flying but has their wings. if you test with only ace pilots, you're likely to overestimate the skills of the average user. indeed, Boeing had assumed pilots would be quick-thinking enough to breeze through a checklist and compensate for MCAS in seconds, which wasn't the case even for seasoned pilots.

also, I imagine the job of a technical pilot is more to assess the behavior of the hardware through a series of tests, rather than regular flying. like how QA testers of a CAD software might not be CAD wizards, but know the product inside and out.