I am new on this forum. However, I have been a student of various systems in the past. I don't trust these statements. Based on the following flight path and pictures posted on here of the projectile, I believe (and I could be wrong) that this was a test of a gen-1 Hypersonic glide vehicle by India. They knew that in the peacetime, there won't be any retaliation, this test also tested PA/PAF's ADS.
I don't think there was any mistake behind it. The object sort of fits the size of a gen-1 HGV, supported by the size, speed and flight path.