As far as distance goes, unfortunetly the rules are rather strict, but if you come from behind a rock corner, and one is 20' in front of you, you can get some hefty fines, even tho you did not intentionally attempt to be within the limits
You are correct. Fortunately, an officer can utilize some discretion in these cases. In the scenario you illustrate above, I would personally never write a ticket as long as the boat did what it's supposed to do as soon as it sees the animal: stop and let the animal go on its way. Take pictures if you want, but let it be. The only way an unwitting vessel operator should be cited - IMO - is if they're operating negligently in some way, at a higher speed than conditions warrant and/or without looking where they're going
Conversely, I've written tickets to people who put their engines into gear and - even very slowly - "followed" the animal to try and find some better camera angle or additional/personal moment of zen. Even if the animal doesn't seem to be alarmed, frightened, or swimming quickly away from you, you could be "herding" it in a direction it may not want to go, separating a calf from its mother, pushing it against a bank that you can't see, etc. People always try to get close to the buoys in AK where the Steller sea lions are hanging out - usually scaring them off the buoy. And in fact, the may have been "hanging out" there because there was a killer whale nearby, so duh - way to help out nature!
If memory serves, the law actually says something to the effect that any type of "pursuing" which interrupts the "breeding, feeding, or sheltering" activities is considered a "take" under the act. Unfortunately for the animals, the MMPA is pretty toothless and easy to circumvent by any would-be violator, so it helps if the animal is likewise threatened or endangered and, thus, covered by the Endangered Species Act. Of course, you almost always have to witness the violation personally, because even photos are never great proof, especially on the water, where judging distances can be dicey.
I was glad to see you write about stewardship, and to be honest, boat owners (power or sail) aren't even ther worst violators here in the PacNW.
Kayakers (of which I am one) are. They seem to think that their ultra-stealthy activity is virtually unnoticed by the animals, which is far from the case - they "herd" and do all the same things I just mentioned, just like a bigger boat does. Except they do it more often because they mistakenly believe that they have no ill effects on the creatures.
Ron