Based on what I see, and the late timing I would not repot unless it is necessary!
Once the root ball is well established Mume are more forgiving but initially when transitioning from thicker roots and older soil it pays to be careful.
I expect the schedule applies to well maintained trees in routine care!
If you are well trained, experienced with mume and have facilities for aftercare that opens other possibilities. However, why take a chance if the tree is doing well and the current state appears to reflect that.
In your climate, like mine I would repot early and protect from frost, rather than wait until risk of frost is past. Likely never make that window with Mume.