The problem is, despite knowing the buyer's name, one cannot assume that the same entity gave the bond to a particular political party.
Based on uploaded electoral bonds data, there’s no way to match bond donors and recipients. One knows X purchased a bond worth Y. And political party A cashed a bond. But A cashed X’s bond? Only SBI knows by matching the bond number of the purchaser (donor) with the one cashed by a party. This implies the government knows it, too.