Sure, be skeptical, but then maybe say something like "I have no evidence for this, but I believe his manifest enthusiasm can only be explained by the fact that he's trying to manipulate the stock price to his own benefit."
Sure, it sounds less rhetorically convenient, but it's more honest.
I think this is the video I'm remembering, but he reused charts like this a lot https://youtu.be/p0kFZ9CVLNg?t=512
see this for some real-world testing, there's lots like it and the results usually skew a certain way for each car. for example, there's about a 20% delta in epa vs. tested range for the tesla y LR and mach-e standard range in his chart. the tesla artificially looks 20% better! and this delta was well-known at the time of his video https://insideevs.com/reviews/443791/ev-range-test-results/
to your question about conflicts of interest, owning a stock is a conflict of interest. nobody needs to show that something is happening inside his head, the circumstances exist and that's it. I think he's usually pretty good and I still watch the videos, and he trades on his reputation and I still regard him as a good source. but I'm still glad to learn that he's sold the stock