It's not misinformation. I got it from our veterinarian, and from a practical, real world framework, it is true.
Had a cat that got a severe reaction to a rabies vaccination, which resulted in siezures which necessitated making the cat an 'inside' cat. after a few months the cat started having problems like oral, rectal, and ear bleeding. The vet traced the problem to a near total absence of ascorbic acid. I said that I had read that cats could make their own. She laughed, and said that the miniscule amounts that a small percentage of animals may make is negligible. She prescribed grass cubes that were available at pet supply shops. The grass cubes worked within about two weeks.
In post 479 I asked why the same mutation is responsible for the inability of great apes, including people, to make ascorbic acid. How can this be explained without the common ancestor stuff.
IN #495 ES said that no mammals make ascorbic acid. Astonished, I provided a reference listing which organs make it in which mammals, and asking where he learned this "fact"
He replied in #515 from his vet treating a sick cat. "She [the vet] laughed, and said that the miniscule amounts that a small percentage of animals may make is negligible".
So, we go from a sick cat doesn't make enough to no mammal makes any! In fact, Pet Place (ask a vet) says it's only needed by cats and dogs with liver disease!
Your vet is a nitwit.
http://www.felinefuture.com/nutrition/bpo_ch8a.php
Although vitamin supplements are sold for cats and dogs, I challenge you to find a veterinary organization that recommends vitamin C supplements for housecats.
I have two 16 year old housecats that have never had anything but Cat Chow.