I believe you are correct, if you don't require special access or impair the public in any way. However, like most federal agencies, rules are a moving target and how the rules are interpreted by the "enforcement rangers" is in direct proportion to the amount of starch in their uniforms!
The only issues I can remember in years of photographing in the National Parks both happened at Mt. Rushmore, once where the ranger cornered the two of us since he saw dollar signs (permit fees) with our tripods and several years later when the newby ranger made a scene with the tour group hired-camera operator doing a bus load of foreign tourists off to the side with the heads in the background.
Both would have made TJ and the boys roll in their graves!
Otherwise, the informed rangers won't make it an issue. Follow the rules and be kind to other visitors, keep a copy of the rules in your bag (just a few pages of legalese), and have a blast! However, don't use my tripod holes or Ansel's and find a new and unique POV to separate you from the millions of photos of the same on Flikr!