An option to keep generative fill to the selection

Just had an embarrising momment with a client because a generative fill changed something outside of my selection. 

Every other tool in photoshop only effects the selected area, having generative fill effect areas outside of the selection is strange and confusing. And in this case leads to errors.

Can I have an option to make is stick 100% to the selection, please?

I'll happly deal with whatever weirdness this creates if it means not having sirpirse errors!