Not even half of Tengyun will be complete with this test. Tengyun should also be able to takeoff, climb to 100 km or so and then the Second stage rocket with the payload would take to orbit.They mentioned one of the complication of hypersonic vehicle separation is shockwave interference. Well the Teng Yun project publicly demonstrated it with a free flow separation test in hypersonic wind tunnel. This whole thing maybe a more complete test, real flight with control system.
Though Teng Yun TSTO is not supposed to separate at really high Mach number, more like M5 to M10. Right at the speed limit of it's air-breathing engine (RBCC/TBCC). Definitely not at Mach 20.
This test would contribute to the reentry and descend portion of Tengyun project/program ( if at all it is a TSTO related test).