Lets keep in mind, Shui's record was for the worlds fastest Conventionally Configured Turbine Aircraft.

This means an internal ducted engine with pipe, retracts, and a conventional planform (not a delta).

This video of this delta has been around a long time, and it's been compared to Shui's run many times, but it's apples to oranges, you can't use them for comparison, same with the DS gliders, far from the same thing