How does the "History" genre work with documentaries

The IMDb guidelines for History says:

Primary focus is on real-life events of historical significance featuring real-life characters (allowing for some artistic license); in current terms, the sort of thing that might be expected to dominate the front page of a national newspaper for at least a week; for older times, the sort of thing likely to be included in any major history book. While some characters, incidents, and dialog may be fictional, these should be relatively minor points used primarily to bridge gaps in the record. Use of actual persons in an otherwise fictional setting, or of historic events as a backdrop for a fictional story, would not qualify. If the focus is primarily on one person's life and character, rather than events of historical scope, use Biography instead. Objective.

This seems to be written with fiction in mind; if we were to extrapolate to documentaries, this would suggest that only documentaries covering the same type of historically significant events would be covered. But how does this apply to something like film or music history? Presumably a documentary about 50s B-movies would not qualify as History because it's not "the sort of thing likely to be included in any major history book", but something like a documentary about the first talkies might? What about the middle ground, like this? https://www.imdb.com/title/tt18206786