When grammarians say "passive voice", they are generally referring to a sentence in which the subject of the sentence is the object of the action of the verb.
I was hit by the ball John threw.
On the other hand, there is another class of sentences where causation is just plain fuzzy. The agent is missing.
The cup broke.
In some languages, that's just the way the verb "broke" works -- or worse, the agent himself can be held to be the victim of the broken cup. The sentence "I broke the cup", when translated properly to Spanish and literally back, returns as "The cup broke itself at me"!
In English, the agentless sentence "the cup broke" is acceptable, but problematic. When spoken by a person who was there, without further context, that sentence implies that the speaker is intentionally dropping information about the "agent", the person who broke the cup. The omission is likely to be a passive lie.
In addition, that type of switch can flag an active lie. Active liars have a tendency to disassociate from the part of the story that they invented, so that things just happened, rather than being done or directly experienced by the liar.
On the other hand, when the speaker was not personally there, there is no such implication in a sentence exhibiting lack of agency. When I say that the gas main broke downtown, or that a bomb was dropped on Hiroshima, there is no reason to infer that I was the one that broke teh main or dropped the bomb. This lack of agency is common in historical writing, especially where the identity of the actual agent is not clear from the record. One does not know, for example, whether it was Ronald Reagan personally or one of his staffers who came up with the Solomon's solution in the following anecdote -
In February of 1982 a Christian protester named Mitch Snyder began a fast to protest the naming of a nuclear submarine "Corpus Christi" - Latin for "Body of Christ". Of course, the name was chosen by following the pattern of naming submarines after U.S. seaports, not as an affront to any particular religion; the U.S. Department of the Navy refused to change the name for over 40 days and 40 nights. Snyder was becoming weaker all the time. Eventually, the word came down from the office of President Reagan - the name of the submarine had been changed. It was now, "City of Corpus Christi".
Some fiction writers object to the use of this fuzzy agency in narrative summary, since it reminds them of what liars do. My suggestion for other writers is to be careful about your method of switching focus, so as not to trigger this association. If you are keeping tight focus on a particular person's POV when you are writing your scenes, then make sure to present your summaries from that same POV, as modified by the time and space element involved. If the POV character knew the agency of the act, then include that information, but only if it doesn't overcomplicate getting your reader from scene A to scene B. Definitely do not include information in narrative summary that your POV character couldn't have known across the time and place of the summary.
On the other hand, if you are writing primarily in an omniscient style, just be consistent in your practice.
Hat tip for advancing the subject, Tricia of NTSFW.