Hey that's a really good point lets see what scientific literature says about that:

4.1. Evidence Considerations-To date, only sixteen studies have looked at actual health-related outcomes in dogs and cats fed vegan diets, as opposed to performing nutrient evaluations of diets. However, the majority of these studies utilized small sample sizes (ranging from 2–34 animals) for the direct investigation of outcomes. Whilst survey studies evaluating guardian-reported outcomes generally encompassed larger numbers of animals, these are subject to inherent biases due to participant selection, as well as the reliability of lay people making judgements around somewhat subjective concepts, such as health and body condition.

It then goes on to say:

The risk of bias assessment performed on the experimental trials suggests, at best, an unclear risk of bias across the studies. There were some particular aspects of poor performance (or reporting), especially around randomization and blinding. This has been reported previously in animal studies [42], where researchers have probably not taken on board some of these important facets of experimental design and reporting to the extent that human clinical researchers have [43,44]. This remains a major concern impeding reproducibility, and where internal validity of the study is impacted, also leads to wastage of animal and financial resources [42].

Seems like the science backs your claim up partially. I would call it bias instead of lying though.

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9860667/