I'll do some research on this one, but IIRC there is a regulatory requirement that all CFI's complete the training. I'm not sure if there is an exemption for "inactive" CFI's.

In case there is no exemption, I probably wouldn't admit to having not completing the training. This is probably a well intentioned survey, but they are still the governement...if some upper manager doesn't like the results, they may punish/violate everybody who admits to not having done the training.

Safest thing to do is knock out the training before you respond to the letter...that's my plan.