Bayern Munich got problems with finding a good sticker and a player to finish balls for them that's the reason for Tuchel to ask the team to hire Kane. However, in the last time when they hire Sadio Mane, he had a perfect performance in Liverpool and scored many goals in that team but when he joined Bayern Munich he couldn't have a good performance that's why I think there is a chance to see the same story about Harry Kane.
Even though Harry Kane could perform better than Sadio Mane in Bayern Munich but it is absolutely possible to see the same story again. Just to remind about Lionel Messi poor first season with PSG. Even a top world class footballer could fail to adapt fast so they have to wait and give him a second chance if ever that happened.
Tuchel wants an excellent number 9 to drove the team to victories, this point is totally agreed by Bayern Munich staff, otherwise recruiting a number 6 isn't considered as a priority to them although Tuchel insisted also on that point.
Of course there is no guarantee for any player to start playing amazingly after they join their new team. But when it comes to Messi's situation it was a little different as well. I mean he was used to playing according to Barcelona's game plan for long years. However PSG's understanding of game plan was way different than Barcelona so Messi didn't adapt quickly.
Because he was used to getting passes and distributing to his other teammates to create dangerous attacks and goal chances. But he wasn't able to apply the same things at PSG in his first times. But after some time he started to get used to it and performed really great.