FBC-P 410.4 Substitution only allows that restaurants serving water free in a container or occupancies serving water in a dispenser can use this for 50% of the required water fountains. There is no exception for a two spouted drinking fountain. There are what is called a hi-low drinking fountain that is two drinking fountains together that can count as two drinking fountains.
The exception is clarified in 410.3. A high-low fountain is acceptable which you could say is one fountain with 2 spouts which would count as 2 fountains. It has to be a high for standing and a low for wheelchair.