First flights are basically never more than a basic functionality check of take-off and landing configurations. (Note that there were no pictures of it with the gear retracted, because that's also typically something you don't try on a first flight.)
I mean, if you trust the math, you can just YOLO it and see what happens. The FAA is the major hurdle there though, because they don't trust the math, nor do they have the ability to really analyze it. So how far they have to go is mostly up to what they can get approved for, and how long it'll take to provide the data the FAA needs to give them the go-ahead.
It's fairly likely they'll find things that need changing along the way, which may also result in the need for additional regulatory oversight, so, double impossible to know if this will be flying at design speeds in a year or ten years or ever.
I'm sure we'll get a HN post about it when it does however.
It's not really about trusting the math, it's trusting the math has been implemented on that real-life aircraft over there. The truism about not wanting to fly an aircraft design which relies on a function being Lebesgue-integrable but not Riemann-integrable is not questioning the mathematics.
