The use of a camera does show up that these Witnesses did not have much real depth of understanding of the creation/evolution debate. The control aspect is also evident. From that perspective I think it is great work.
On the other hand, I think that if one's goal is to sow seeds of TTATT then doing so without a camera would be more productive.
Regardless, often when a Witness is faced by someone with knowledge of a subject and the ability to debate the matter then they eventually want to move on. Even when having a discussion in a reasonable manner, if it is obvious that the person is not coming round to some acceptance of the JW POV then most dubs will move on - no sale here. When on the doorstep it's easy, you just say "I have to go now". With the carts it's less easy, they have to be pretty rude and pack up. Showing that on camera is pretty telling.
I hope the producer, "dontdoasyourtold" carries on with some videos. I see they are filmed in Bristol and I know at least one friend of ours who does the metropolitan witnessing work there and I would love to see what happens if she was engaged in conversation!