I don’t know the answer but I suspect that Teva asked the FDA for some kind of written response by the end of January because Teva has to answer NVS/MNTA’s patent-infringement complaint in the US District Court in early February.
If my supposition is correct, then your observation, “I don't feel this letter means a darn thing,” is on-target, IMHO.
“The efficient-market hypothesis may be
the foremost piece of B.S. ever promulgated
in any area of human knowledge!”