In film, a 'frame' is a single photographic exposure. A movie typically consists of 24 or 30 frames per second.

http://en.wikipedia.org/wiki/Film_frame

By contrast, a "shot" is "a series of frames, that runs for an uninterrupted period of time."

http://en.wikipedia.org/wiki/Shot_(filmmaking)

Personally I took the phrase 'frame-by-frame' to be a figure of speech.

"A figure of speech is the use of a word or a phrase, which ascend from its literal interpretation."

http://en.wikipedia.org/wiki/Figure_of_speech

I think the comment author was just trying to emphasize they were trying to be thorough, a bit like when police say they will search an area with a fine-toothed comb. No reasonable person expects the police to use actual combs.

Frame is a technical term that has a precise meaning in this context.