what more proves do you need to make it ''substantiated''
regards
First and foremost, your recipe is an incendiary, not gunpowder. There's no sulphur.
In general terms, you've assumed that since a precise recipe is present in two sources, that the "earlier" source is the progenitor source. This is an assumption and remains so until proven otherwise. Since the chanakiya is strong with you and you're a fan of circumstantial evidence, ancient gangetics - even with apparent progenitor knowledge of gunpowder (SULPHUR-LESS THOUGH, EVEN BY YOUR OWN REFERENCES) - did not appear to make use of this weapon formally, apart from your fanciful interpretations of fireworks scaring elephants. How can knowledge of gunpowder sit idly with a civilisation for centuries? The Muslim empires of the region actually first utilised it properly - and that was after relearning its uses from Mongols and medieval Chinese (not from recipes in ancient Vedic texts). How is it possible that such a documented powerful mixture was not utilised by the Vedics?
The Chinese knew of a THREE ITEM mixture creating a combustible compound even before the arthashastra was written by a whole century. The Chinese formalised its mixture and applied its uses over the coming centuries while the vedics next door just sat on this knowledge - is it really possible that vedics knew such detailed recipes (sulphur-less, I must repeat once more) and didn't know what they were for? Or is it more plausible that some miscreant inserted this knowledge retrospectively when more modern Indians suddenly started using gunpowder properly?
Clearly walking suicidally into a fight with bare fists despite having access to advanced military technology is not a phenomenon restricted to the 15th June 2020 in the Galwan valley!
Now - here's the kicker - History of India, p23, John McLeod. - The Arthashastra itself may well have had interpolations and additions up to 500 years after its original writing by chanakiya.
If we analyse your theory in circumstantial terms, is it more likely that vedics sat on this knowledge for hundreds of years without using such a thunderous and terrifying weapon? Or is it more likely that they never actually knew about it, incorrectly copied its recipe (without sulphur) later from the Chinese and inserted it retrospectively into their main national treatise on statecraft (a perfectly reasonable thing to do btw - I'm not judging negatively such an act)?
Indeed, retrospective Wikipedia editing is one thing Indians can believably claim to have invented and perfected long before anyone else.