The Skiller can decide whether he wants to give up to 5 minutes free. Its good in order to check if they match. And in case that the 5 minutes free was enough for the whole service the user can tip the Skiller and everyone will be happy

How do you prevent people from abusing this 5 minute grace period?
We don't. its up to the Skiller to give them. If the Skiller notice that the user is not serious he can end the call immediately.
I see. Is the call charged per second or?
It's probably paid per second yeah.
They did say that the first minute is free, where did you see 5 minutes? Maybe I read it wrong

Maybe we all got lost in the whitepapper

I think thats something that someone from the team confirmed recently,about Skiller having option to give up to 5 minutes free.
That's an excellent strategy to get people to try your product and see if it works for them, not having to spend a lot of money/tokens if it's not really what they wanted.
True,those Skillers who are confident about their ability shouldnt have issues with giving few minutes free,it should pay off in the long run.
Agree. Nice to have couple minutes free to tryout.