I wish coaches and GMs would take a course and have to be tested on what Corsi and the such
actually means instead of all these incorrect narratives being spouted off of it. It's a shame there's not enough time to go through 500+ publications dating back to the early 2000s and figure out what has evolved off of what,
but I encourage you to do so if you're interested.
Luckily, I can point to how Tanev performed last season versus this season:
Personally, I am happy that Tanev has grown into better than he was last season in terms of shot metrics. Typically you don't get that with players going from age 25 to 26. Still, a -15 to +11 goals on metric isn't something to be totally trusted. If you wanted my honest opinion, I think Tanev's real talent lies somewhere in the middle of these two drastically different seasons. If anything, the only consistent thing between these two seasons is that Tanev draws a ton of penalties (which is a good thing).
I also think playing with the likes of Copp, Armia, and Lowry vs Thorburn, Burmistrov, and Petan is more of a complement to what he brings to the game.
EDIT:
I've argued these lineup decisions before in terms of what optimal lineups bring to the table in terms of xGF.
And I sincerely hope you don't believe Tanev had a good 2016-17 season - because that clearly wasn't the case. Arguably, there's not much to use from to predict that all the sudden he would post a 8-goal season (of which 3 came as a hat-trick) versus the 2-goals he had last season, other than "he shoots a lot".