Fons or Alfons as it is called in Egypt, is not truly the Indian Alphonso. The taste, color and aroma are different. Although, the leaves are very similar and could hardly get distinguished. Furthermore, the Fons seeds are polyembrionic while the Indian Alphonso is monoembrionic. Tree shapes are very similar.
When mango seedlings were brought to Egypt from India, they were brought in groups. Each group had similar varieties in terms of shape. The one suvived from the Alphonso group was the one they call Fons. And it is misnamed Alphnoso until now. I believe this cultivar is actually the Pairi variety.