Aren't we confusing 2 different things here? Visas you get through employment - eg H1B - are specifically non immigrant visas. You are not an immigrant when you

Aren't we confusing 2 different things here? Visas you get through employment - eg H1B - are specifically non immigrant visas. You are not an immigrant when you are in the US with an H1B. Are they restriction on green cards too? I thought once you got your GC you didn't lose status for being fired.