According to the data on the Seachem site, this is filter media and does not come with bacteria. You use this in the filter and it does...what Seachem claims presumably. But the bacteria that will colonize it will come from the aquarium.
Seachem Matrix (and De*Nitrate [smaller pieces of rock]) is merely pumice stone (a type of lava rock). I've purchased it in the past and it is always dry as a bone so as Byron points out, bacteria population comes from the aquarium. If you're looking at this for bio-media, check out General Pumice Products for a more cost effective pumice stone. (I am not affiliated with the company in any way).
The individual in this video has some inaccurate ideas as to how bacteria and filter media work and interact. Matrix is sold dry, so his liquid Matrix is water (tank water apparently, which he says contains bacteria) he has added to the bottle. This is not going to "condition" the Matrix. Once Matrix is in the filter in an aquarium producing ammonia, the bacteria will colonize and multiply according to the amount of ammonia it has to feed it. In the absence of ammonia, the bacteria is not going to reproduce anywhere.
Matrix may or may not support more bacteria than other media, but media is media and nitrifying bacteria can only exist at the level according to the ammonia supply (and then nitrite for the second phase). This will occur in any filter and the substrate, filter or no filter, regardless of media. The thinking prevalent among some hobbyists that the more filters, or the larger the filter, or the more "better" media it contains, is somehow going to increase biological filtration is a myth, at least in a balanced system--obviously a tank out of balance may benefit from more filters but that is a state one should never allow the tank to reach.. The nitrifiers will appear, colonize surfaces somewhere, and do their work. With live plants in the tank, this is unnecessary as they do the job differently and frankly better, but the bottom line is that nitrifying bacteria do not increase beyond their food source, and they can go into a sort of hibernation if the food diminishes. The temperature and pH can also affect these nitrifying bacteria.
As AbbeysDad said, manufacturers, even the more reputable ones, have all sorts of products that are expensive and claim to do "x" but most are little more than hype.
Ah, he has 'pre-conditioned' the matrix (or thinks he has) by soaking in some undefined solution, but did not describe his process. Any bio-media is best placed in the filter where bacteria naturally colonizes from the aquarium water.
He was also confused about stones changing color suggesting it was done by bacteria. Actually the quality control for Matrix is a bit sketchy as there are some stones included that are not pumice stone, but just plain rocks.
Manufacturers will all say that their product is better than others often due to vastly more surface area. Some will claim their product has micro pores that allow anoxic or anaerobic bacteria to oxidize nitrate into nitrogen gas. Well, maybe...or maybe not! In any case all commercial bio-medias are merely hard surface space for bacteria to colonize and as much as the filter is a nice place, any media there is typically dwarfed by the surface area of the substrate, be it gravel or sand.