I think the main language to emphasize is: If you were an employee subject to the DOT hours of service limits, that percentage is 80% for business meals consumed during, or incident to, any period of duty for which those limits are in effect.
Which, for ATC would be 24/7 because you're recallable at any time, or at least during your entire shift. It looks like the 2017 revision is still the current version and the language hasn't changed.
