Not sure, but he did follow Pellers closely during his tenure and was basically the Man City correspondent for Fox Chile in 2013.
Wouldn't consider him as reliable as say, Maks Cardenas, but he's not just making shit up either.
I think Falk is wrong in his assertion about Gnabry being the end of Bayern's interest. SportsBild aren't reliable anyway, but Gnabry seems more of a Douglas Costa replacement if anything.
That said, Sky Sports have had a shocker of a summer so far and are about as trustworthy right now as a magic 8 ball.
Bayern have a strict wage structure that could not sustain an Alexis Sanchez even if he wasn't looking for more than he currently earns. It's not an option for them and, seeing Sanchez has wanted City from day one, I'm fairly certain he hasn't been an essential part of Ancelotti's plans for some time.