Are Sky Sports in Germany reliable?
If they're reporting this as a legitimate rumor, no lol
Although I do see a scenario where Goretzka may consider leaving at the end of the window. Konrad Laimer is starting over him right now, and it sounds like Tuchel wants a true 6 to play next to Kimmich. So I think Bayern will be open to selling him and he might be willing to leave if he's not a starter after their first 2-3 matches and sees the writing on the wall.
But that is a long way from right now where a lot of things can happen until we get to that point. It's something to reevaluate in 3 weeks.
Would Goretzka want to join Juve over other clubs, and would be Juve be willing to pay Bayern's asking price? Those are the 2 bigger issues for Juve.