I've done shelves with 90 degree support brackets below before (not sure how the ones in the picture stay up without them
). I've got one in my A/V closet supporting MUCH more gear than I can lift at once. and I've got a test equipment shelf mounted to the wall over my work bench that gets a LOT of heavy stuff placed on it.
Back when I was into radios only I had some real nice looking brackets, and shelf wood ready for such a project, but never got to it...
Brackets or however they did it in that picture you will have three fundamental issues with putting TV on shelves like that: Finding shelf wood that deep/sturdy, the leverage factor of the depth adding extra strain to the hardware, and finding 90 degree brackets deep enough to do the job.
If I ever go with wall shelves it will only be for radios and my smaller(shalllow 50's-70's sets)/lighter TVs....As it stands the radios I'd put on the wall would free up a good floor standing shelf I could use for TVs.