Lehmann, 51, told talkSPORT: “I don't feel that because when you come from Birmingham, a team out of the Premier League, then you expect something of him.
“I like him as a player - his posture, his physicality, but also his technique. And he can score goals at a very young age.
“So it is good for the Bundesliga that, all of a sudden, young English players go the other way round.
"Before it was always German players going to England, now it is the other way around."
Lehmann added: “It's good for his personal experience, his development, just in case he goes back or plays for the English national team.
“But, right now, I guess he wants to experience the fantastic atmosphere of the Signal Iduna Park because due to coronavirus, there were not many occasions when people were allowed to come to the stadiums."