It may have been true during the days of CRTs. I have had a lot of pets and don't remember any of them showing interest in the televisions whatsoever, other than a source of warmth. And that is definitely no longer true.
On Instagram we received hundreds of pics submitted by viewers of their cats watching Kitten TV, it became a meme.
This is the problem with this kind of thing so often, people observe something and an explanation that sounds completely logical gets spread around.
Not sure about dogs, but cats definitely could see a plain 60Hz CRT display... atleast some of them anyway.
For example, this spectral comparison implies there is a rather large difference in the color experience of watching CRT vs LCD. Very pronounced and spikey red component vs smooth gaussians. Canines are notorious for issues with red colors.
https://www.researchgate.net/profile/Alireza-Shahsafi/public...