I don’t trust that at all. They just say that so they can justify more funding.
Remember the Millennium Challenge 2002 where the US got completely fucking clobbered in a simulation of the War on Terror so they just cheated and changed all the parameters to make sure they won? Remember that the military has total control over these exercises and has manipulated them for propaganda purposes in the past. As such this should probably just be ignored, or else engaged with with extreme skepticism, from the perspective of understanding what they hope to achieve by saying this.
It’s possible that the conclusion is correct but if so only because the military is so full of bloat, corruption, and profit-focus that throwing more money at it could only make it worse.
