No, it's not. If someone has no stake then they have little incentive to be right or not. And in the long term, it's better for them to try to be right because they can brag about their historical accuracy when making future predictions.

But for people that have some risk in Tesla (this firm's ETF is over 10% TSLA), then they have an incentive to pump the price up, even if it means lying. If they can pump the price they benefit. There is no reason why their advice should be trusted if their advice is toward the direction that obviously benefits them. Now, if someone had 10% of their money long TSLA and they said the price was going to fall, then I would probably trust them because that advice isn't directly benefiting them (or I'd be very suspicious that they had some other scheme going on).

It does make them a biased source of information, which is the original point. Why would they ever publish a pessimistic report about Tesla and risk the stock going down even 0.005%?

Would you go to a doctor who had to pay you if he gave you a cancer diagnosis? How proactive do you think he would be to screen you?

That's not their money, though. It's the money of their customers who buy their ETFs.

They have a strong financial interest in pumping up Tesla stock, so I don't know if their "analysis" is much trustworthy.

They're not risking their money. They're risking clients' money.