All that means is that the ends (and not the means) are the determining factor.

A private company can have plenty of legitimate reasons to film in public spaces, and to incidentally film people.

Flock's ends are to explicitly track people, and to use that data to accuse them of criminal activity. Those are the ends that the 4th amendment is written to explicit protect us from that, and not exclusively from governments, either.

> The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.