IW has always been slow an Fed has won this event 5 times so far. IW suits Federer even more than it suits Thiem.If it were a true HC then yes.
So I'm not sure Thiem is the best opponent seeing as it's slowed right down. Suits his game style more than a few other guys, as we've seen with the results.
People assume that just because it's a slow HC, it means Fed is helpless on it, forgetting that IW is actually Fed's second best masters event.