In this case Amazon would be seeing who was voting.
It says that the cameras would "keep an eye on the ballot boxes in the off hours between counting" which seems... perfectly reasonable to me.
It looks like they aren't anonymous?!
First, go through all of the envelopes, reading the names, and either side can contest ballots, which are set aside.
Then, the uncontested ballots are removed from the envelopes and counted.
If the vote margin is less than the number of contested ballots, that kicks off some kind of remediation process.
Just look at this thread and how much confusion over what the cameras are recording.
> During this portion, the NLRB will read off each voter’s name and both sides will be allowed to contest ballots, likely based on factors such as whether an employee’s job title entitles them to vote or an illegible signature. Any contested ballots will be set aside.
>...Amazon had sought to place a video camera in the NLRB’s Birmingham office, where votes will be tabulated, to keep an eye on the ballot boxes in the off hours between counting, according to an NLRB order denying Amazon’s request. The camera feed would have been accessible by both Amazon and the RWDSU.