Jaba, the Smith argument was debunked years ago on exactly your premise.
The Uni of Texas claim is to mimic GNSS to "capture" a basic gps. Does this represent a security issue? Can a terrestrial signal be ignored by antenna mounted on upper surfaces of an aircraft? Does that then create issues with terrestrial L5 networks? Is the threat scaleable?
At this point I would call this as a good party trick. Open field testing at typical aviation environment is required.