Or perhaps it's user error. I've provided three screen captures for this one. It's strange. I've noticed this issue before so I went to test something simple and easily repeated it.
In action, I access one an axis which controls video media. I have autokey on, and on frame 1 simply change the x rotation from 0 to 10. I then choose an arbitrary time ahead in which there are no keyframes in-between, set another key frame for 10 (a flat graph), but rather than have 10 degrees hold in the duration between, I see animation occurring in this section. The pictures provided show exactly what I mean. I've recreated this by adding a third key frame at, again, 10 degrees, and still find there to be some kind of animation. Why?
The default keyframes interpolation is Bezier. So there is some anticipation from 1 keyframes to the next. There some play in the movement. If you want straight linear keyframes then open up the keyframes editor and select the channels and switch the interpolation to Linear. Then you will get no additional movement.
Senior Editor - Autodesk Smoke
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Thanks for the help Brian. I'm glad I made it clear it was likely something I was doing. This is a perfect example of someone who's used to editing in applications where, if key(i) to key(f) are the same, no animation should ever occur. This is thinking outside the box for me but it's useful to know. I'm changing that preference since I'm more of a linear kinda guy...