It was my understanding per the Asset Store Terms, that assets purchased off the store could be used in Commerical Games. But this guy on youtube is insisting that if you do use them in a commercial game, you have to negotiate a royalty deal with the asset creator. I’m not sure where he’s getting this from, but can someone, preferably someone official, explain why this would be true or why not definitively?
Thanks.
Another good reason not to believe any random bloke on youtube. Then again, wait a few minutes and I’ll upload a video about a bridge I have for sale. 
That youtuber is talking about something he has NO clue about. He is completely wrong - other than suggesting to choose to provide credit for asset creators. However this is the developers choice.
Everything else he says is completely wrong.
Though in some cases contacting the creator of an asset might be worthwhile, not for the reasons he stated, but for joint marketing opportunities. The asset creator gets to point to a released game using their stuff for marketing credibility, and extra publicity for a game never hurts
Heck yeah - good point - just not for permission to use OR to consider rev share 
The video guy stated today he’s doing a new video tomorrow with ‘official’ word from Unity itself. So I’m looking forward to seeing what is going to be officially stated.
You should just ignore him; it’s highly unlikely anything he says is based on reality. If it’s not directly from Unity, then it’s not official. This is beyond idiotic…like claiming that if you buy a game, you then have to give extra money to the game creators based on the number of hours played. You already have your official answer, as posted by TonyLi above.
–Eric