What does that mean?

it is used to prevent illegal classes

What does that even do? The description is really vague. I have Amalgamation Classes mod. Ok. SO, what does this "exclusions" mod really do?

Intentional

Exclusions is causing Blademaster skill "Slash" to not recognise combat knife as a valid weapon, despite it specifying below the skill description that combat knife is a valid weapon for the skill. (the yellow text)

I see. Thanks guys. I think I experienced the types of things you're describing when I removed this mod from my list.

what could also be: if you run without exclusions at all the game may take a loooong time to start up

As Xpand said ... nothing would probably crash (though some things actually might because of animation stuff) but the balance would be way off for sure

I can answer this: It is. The specs themselves no longer have any exclusions in them, so they'll be waaaay too common if you aren't running this exclusions mod or the old one.

Is this a hard requirement for your Amalgamation classes?