Mxsmanic plays with toys writes:

How can you make that statement?

When it's true.

When have you experienced the real thing?

It is the real thing. It's all just words. The words in simulation are
identical to the real thing. ATC communication is one of those things that
can easily (very easily) be simulated with 100% realism.

How many private pilots do you know?

Probably half a dozen or so.

How do you measure their ATC knowledge?

I can ask them questions and count their errors.