The shortest explanation: performing Kolmogorov-Smirnov tests does not make a method “tangible”.
It is simply the application of an existing statistical tool.
The method remains theoretical, even if used, like a key does not make the door more real.
If these tests confirm similarities, they do not provide any guarantee on the robustness of the model under stress conditions.
For example, a KS test may show that the returns of an asset are similar, but never captures market manipulation or liquidity risks of an emerging market.