No it is no a bug.
The Configurator program is designed to give you the flight performance of the aircraft you selected in the Configurator. If you fly a different F-111 model than the one selected, then you will get that warning.
Just start the Configurator and select the proper aircraft or auto select for the model you are flying and the warning will go away.
There is also a Default setting in the Configurator that will work with all aircraft. This setting applies the same flight characteristics to all models. It is a little less realistic, but makes switching models a little easier.
This way we can satisfy the ‘Sunday Flyer’ and the ‘Serious Flyer’