Difficult to believe these rumors anyway he very good player only 22 years old but after seeing how many players failed to make impact in PL after coming from Bundesliga it should send a warning Bundesliga have no defense is too open.
You're right it is hard to gauge attackers from the Bundesliga. Must admit I don't watch it much, but did have a spell of watching the games in lockdown in 2020 and what's obvious is how open the teams are. Was seeing teams go to dortmund and Bayern high pressing, pushing the fullbacks forward and splitting the CBs, a dream for attackers with a bit of talent playing for the top teams.
Seems a lot of the defenders lack pace as well, Sancho looked relatively quick in the bundesliga but moves like a 60 year old paraplegic in the barclays.