Some of the original English and French flints from that warehouse in Nepal are of the spall type. If they all date to within 50 years or so of each other, it shows that both blade and spall types co-existed in the same timeframe. Spall and blade flints have often been found together at colonial forts and other sites as well. I appreciate Hamilton's work and research but have some skepticism about the English not knowing how to make blade flints until taught by some Frenchman. Certainly French blade-style flints were known by the English, and I have a good many French as well as English spall type flints from that Nepal warehouse, so both English and French flints are found in spall and blade varieties. Since I make flints I have found that the rock dictates whether I will make a spall or blade flint. It is almost impossible to work flint and not learn how to strike a blade. If there is a good core with suffiicient thickness, blades are east to strike. As a core gets worked down, I make a flint any way I can, and the last few are spall types. If the English did not know how to strike blades, it is something they forgot, as neolithic tools from England exhibit blade technology.
Spall flints fell out of style by 1800 or so as near as I can tell, though stockpiles of hundreds of thousands of English and French flints probably existed from earlier times, and contained some spall types. I am guessing some old stock got sent to Nepal.