Why would a shop document a box opening?
In short: So its singles carry proof. A buyer can watch the card come out of a sealed pack and see its condition recorded at that moment, which answers "was this really pack fresh?" before it is asked.
Buyers of high-value singles are wary of searched packs, swapped cards and condition that changed after the pull. A shop filming itself does not settle that, because the shop has a stake in the answer.
A documented break is done by someone who holds no interest in the cards, to a written condition standard, with logged custody. The result is a pack-fresh certificate the shop can sell with each documented card, and a record that follows any hit into grading. Recordings are kept under the retention and consent policy.