If I was conspiracy minded I would say it was an effort to knock out any foreign designs from the competition. But I'm not, so I'll just say that it is an incredibly stringent requirement.
I'm not sure why the USAF need it -nobody else needs that type of capability in a trainer- but it looks like they have failed to learn their lesson about overcomplicating matters. They will end up funding an entirely new aircraft that will be way over the top for an advanced trainer and will be eventually cancelled as being too expensive. The T-38s will require another SLEP and then they'll start the whole shebang again.
Why not just pick one of the existing products, guys? They are all perfectly adequate and able to do the job required of them.