My father lives in a development like that. I hate looking for his townhouse because every townhouse is identical. The last time I was down there, "Hey! I just noticed that all the homes aren't perfectly identical. There are two different types of lights on the garages." To which the response was "they will be. A few of the lights broke or went bad, and they no longer make that style. Everyone in the subdivision has 120 days to go to Lowes and buy the exact same model and have theirs replaced with the new style of light. Otherwise, they'll be fined."
Personally, I'd have a hard time dealing with such an anal retentive association.
In your situation, I'd respond with a polite letter stating that they are mistaken and that your lawn is in compliance with their rules, and that they should remove any records to the effect that you are out of compliance. I'd also point out "my rules are that I only ask politely once." After that, I'd go through my agreement with a fine-toothed comb, looking for any loopholes to drive them nuts. "Ahhh, it says I have to keep my lawn raked. It doesn't say I have to remove the pile of leaves." Heck, I'd import them for the kids to play in if I found such a loophole.