It's possible ,but hey our "old Agni-1" { we are expecting to replace them with Agni -1P) can be a greta mimic of DF-21 ...and may be we going to use them soon in tests. Why to create conspiracy wjhen we have suitable stuff.
These are DF-3 ,almost 50 year old now . lightyears difference in technology with current tactical BM of china who are going to be the rival of Indias ABM.
There must be difference inbetn terminal phase speed of RVs of Prithvi and Agni 4/5 , Is our current system able to track RV of as par as Agni 5 whose terminal phase speed is mach 24 ??