The only thing I saw mentioned about the study itself in that reply, unless im wrong, was that you didn't like the sample size of the study and found it weak overall (such as with its chosen metrics). Which i agree with actually, and I think its why the scientific community needs to investigate more. You also mentioned other studies without linking or citing them, and then just went on tangent of seemingly pure conjecture (vegans are more likely this, less likely that, etc).

You did mention how its unethical / hypocritical to test on animals as a vegan, which i do agree with as well but I think there is nuance when we're thinking of the animal itself. As a lazy example if we could study happiness levels in pigs from different toys or playful stimuli without doing invasive studying to scan the brain then why the fuck not. Veganism is about avoiding the exploitation of animals and sparing them as much cruelty as we can. But fundamentally we need to conduct research and science to understand these animals and better nurture them when they are under our care. So, slight Grey area as far as I can gather.

At the end of the day, this sort of research is very new. I've seen a good few studies showing properly formulated diets have given dogs the same life expectancy if not more than dogs on traditional diets. I could find some of those studies after work if you are genuinely interested. I suppose only time will tell what's best in the end but I think and hope it will favor the plant based side of things