It's page 19 and people are still posting spectrum curves when this has been about dynamics all along which are not measurable by spectrum curves. Dynamics and EQ are two different things. So far there's been almost no talk at all about dynamics which started this whole conversation. And no, dynamics are not just getting a clean sound by lowering your volume on the guitar. Dynamics are time based transients a lot faster than the time it takes to roll down the volume of your guitar.
That just tells us that not everyone really understands what they're talking about. Be it someone working for FAS or not. A simple way of explaining this so everyone understands me is: I can match EQ me screaming to have the same EQ balance as a guitar amp and post a graph like that but I'm 100% sure people are able to tell which is which because it will not make me sound like a guitar. EQ is not everything.
This is why I assumed the "difference" might be because of dynamics that the IR is not able to capture or the amp sim not being that accurate with shorter transients or maybe both.