As far as I know, there is no hard and fast rule about this on Equipboard.
I would be inclined to say that if a pro artist is using a product in a demo video, it should count as a correct submission. There are lots of different types of product <--> artist associations. Broadly, I would say we're distinguishing between these two types:
1) The implicit endorsement, where the artist doesn't necessarily talk about an item they use, and the Equipboard community can discover it, and debate the details and accuracy.
2) The explicit endorsement, where a brand sponsors an artist, and has them pose for a photo, write a Tweet, post an Instagram... or do a demo video. Sure, it might not feel as authentic as the other case, but I argue it's still interesting. In fact, the demo videos by artists often go into much more detail, and you can get a great sense for how the artist uses a piece of gear. I'm personally thankful when brands put out really interesting videos about artists and their gear, even if the endorsement is painfully obvious :)
We started Equipboard with the spirit that most artist <--> product associations are interesting, and there needs to be a place on the Internet where this stuff is collected, backed by a super passionate community (you all!) that can talk discover it, talk about it, and keep it accurate. Let's say Equipboard did golf, and someone added this Instagram of Under Armour shoes to Jordan Spieth. Is the endorsement painfully obvious? Definitely! Is this information interesting to some people, and would make them curious about the shoes? Your milage may vary, but I would argue yes!
tl;dr: I vote yes, demo videos count because it's a legit artist/item association.