There is something fishy about this.
The warning letter claims the postmark deadline was Dec 31st.
This warning letter is dated Jan 2nd.
Not enough time has gone by for this to make sense.
Yes, if you give the weasely "received or postmarked by" language in the letter any credence. In all likelihood, the receipt deadline passed (the 31st) and these letters issued immediately. They're not going to nitpick postmark dates unless someone challenges the state in court.