That xG thing seems to be good for nothing to be honest.
It's a big baloney that's what it is. A 16m free shot for a player like Messi or Ronaldo is much clearer of a chance than a 1 vs 1 for some dude playing for Ankaragucu in Turkish league (random example). The quality of a goal coring chance is always dependent on the player who receives that chance. You're telling me Barca deseved 0.5 goals vs Alaves based on this idiotic xG ranking?
Actually, the 'stat world', like opta, or sofascore or transfermarkt or whatever, are just there so that the guys who have no clue about football could feel they have some sort of a grip on things. The only way to discern and understand things about football is to learn tactics. Tactics are the only answer in regards of why things happen on the pitch the way they happen. Everything else is a cheap replacement.
To make a parallel, knowing tactics is like understanding the whole novel The Count of Monte Cristo by Dumas the way it was meant to be understood by the the author in the first place. Following stats is like reading a children's version, 24 pages with pictures included. You either go for the full picture, or you choose to be spoon-fed some random stats who are worth nothing in the end.
Before anyone says something, I understand this sounds arrogant. I don't care though.