Aughh, forerunner of avionics already adopted computer simulation and had done away with physical tests for modeling a long time ago. These days you utilize super computers and analyze wind sheers in millimeter grids which cannot be done with actual physical tests.
This is just the typically unthinking nonsense you keep coming up with.
You think China doesn't have supercomputers to do simulations?
Anyone with any background in data analysis will know the first and most important rule to any analysis work is, Junk in Junk out. If you feed in bad data, your results will never be right no matter how super your computer is.
Why do you think everyone still does real life tests? For lolz? Do you even know how computer modelling works?
You need to do real life testing to learn how things react and interact, what forces are applied and where etc - all the basic rules and values and parameters you need to programme your computer to create a virtual simulation with the same rules, values and behaviour as real life (or usually as close to the real thing as computing power and understanding allows) so you can try things out virtually without having to go through the trouble and expense of real life testing.
But you still need to conduct real life testing to see how your models stack up against reality, and you will want to do that as often as possible.
The difference is that without a wind tunnel that can do such high speeds, the Americans had to make assumptions in their modelling and analysis, and could not check their workings until they did a real life scale model test, which is why their hypersonic glider failed - their underlying assumptions were wrong, so everything based off of that all proved wrong.
China has been able to do real life testing in a wind tunnel at the speeds they were aiming for to see what the actual conditions are like at those speeds, so when they fed their observed figures on their own supercomputer, the calculations proved much closer to reality, and would have helped massively in allowing them to succeed with their design.
The main difference is it would have cost China pennies on the dollar for their tests compared to the Americans, and the set up times would have been correspondingly shorter. Thus they were able to do a lot more regular tests until they got it right. At which point they would then have proceeded to conduction live tests to check for real life factors they might not have considered and/or been able to accurately replicate with their wind tunnels (which appears to be what was being reported upon).
If that is indeed the case, China may well be years ahead of the American team now, who are still busy crunching the numbers from their first, failed test.
The Chinese team almost certainly also have made mistakes or omissions and failed with some of their earlier tests, as you are extremely unlikely to get something this advance right the first time round.
Assuming Chinese and American engineers are of a similar level, the more times China failed with their testing, the further the Americans are behind, as China has all of those failures behind them, while the Americans still has all the steps the Chinese team had to take from their first failed test to their current successful one in front of them.