True, but not necessarily the case here. I'm an introvert who is getting significantly better at acting outgoing when necessary, but being sociable seems to keep a similar level of effort.
Yes, I'm an introvert, too, and I understand exactly what you're talking about. The diff is that how much I'm "drained" depends on the group of people. I have quite a few friends with whom I'm close enough to just be myself, to not "act". They don't drain me at all. I just eventually run out of things to talk about, unlike the extroverts who find more to talk about.
A group of co-workers? That is tiring, because it takes a lot of effort to act that nice.