I am not sure if you call this a bug or an oversite.
I have found that if you have Elephant Foot Compensation enabled and add a brim the brim will not touch the part/model on the first layer. This makes a brim useless.
I would think it would be beneficial for Bambu Studio to disable Elephant Foot Compensation when a brim is selected or at least warn you that elephant Foot Compensation is enabled.
Or vise-versa warn if elephant Foot Compensation is selected and a brim is also selected.