While we are on the same page regarding the point that FDA now officially required TEVA for more work after submitting similar "minor" ammendment to ANDA as MNTA in 2007, I don't completely agree with your conjecture.
I am not sure TEVA asked FDA for official letter. I believe it is in the interest of FDA to give Teva official response to their ANDA due to Amphastar lawsuit against FDA regarding the alleged conflict of interest. Now FDA can say we approved MNTA's, and requested additional information from Teva. Teva is simply using this to its advantage. We'll know how quickly Teva can respond to this "minor" deficiency. It didn't give timeline in the PR, but will have to answer during CC in the future.