The climate of the Indian subcontinent is favorable, with plenty of sunshine and rain, resulting in extremely high grain yields, along with an abundance of fruits and vegetables, so Indians generally don't have the habit of hoarding food.
However, Joseph knew that during the Third Mysore War, Sultan Tipu had twice suffered from not having reserve food supplies.
The British had besieged Seringapatam twice, and the city had quickly run out of ammunition and provisions.