Are people here actually superstitious? I'm seeing an awful lot of "He's good against the Germans, Portuguese players are bad at Barcelona" type comments all over the forum lately. Perhaps Griezmann encountered said German teams when they were at a down period, or perhaps the type of tactics implemented by these teams played to the advantage of the teams Griezmann played for.
Considering that we neither play like Atletico or France, and that Griezmann now plays in an entirely different role in Barcelona, any perceived tactical advantage that Griezmann might have had no longer exists. So I don't see the point of all this speculation, unless you think Griezmann is somehow predisposed to play well against Germans for some odd reason.