this rumor won't be that hard to believe, Tuchel is not a ba coach at all, and to be honest he is better than Nagelsmann, so with bad results coming like losing against Barcelona in the Champions League and another bad result in the bundesliga, there could be a very big chance that they will dismiss Nagelsmann, and Tuchel is available so why not, i can see it happening for sure.
Indeed, since the arrival of Julian Nagelsmann at the start of the 2021/22 season, Bayern Munich's performance outside the Bundesliga has not been too impressive, for example, Munich's failure in the UCL last season was one that attracted attention. Although Bayern Munich still managed to defend the Bundesliga title, Munich's performance outside the Bundesliga maybe a consideration for coach Julian Nagelsmann's career with Bayern Munich in the future.