And then there's this tour operator website which has some same language:
"Q: Can we tour Yellowstone or Grand Teton National Parks?
A: FAA and National Park regulations do not allow low altitude scenic flights operated over either park.
From outside Park boundaries though you will see the entire Grand Teton National Park, the Grand Tetons at eye level, and the region's mountains, rivers and wilderness as your pilot customizes your flight. The aircraft must stay outside park boundaries at lower altitudes except for takeoff and landing. Flights comply with the National Parks Air Tour Management Act of 2000, wilderness area flight regulations and noise-sensitive areas of Grand Teton National Park."
Jackson Hole Scenic Flights web page