It's a stock photo used on a website, did you expect them to go to the actual laboratory they worked with and take one?
I have no affiliation here, but they even listed the company they used for testing so presumably you could call/email them if you want further confirmation. None of this seems unreasonable to me, and I don't think a stock photo is a gotcha for product quality.
Many online sellers post a photo of their factories and workers as a way to demonstrate quality - ie. "look, we make out products with big expensive modern machines, not children doing it by hand". Some aliexpress sellers even post 20-30 pictures of different parts of the production process.
Posting a stock photo is trying to defraud buyers who expect to see the factory it is made in.
There's a lack of forthrightness in publishing a stock photo without a disclaimer. "Lack of forthrightness" is an anti-signal. Stock photography on a commercial website is an anti-signal.
>They expect us to be swayed by a stock photo of a laboratory?
I don't think any picture of a lab would have any meaning to me, whatsoever. Is the product legit tested? That's all that matters. I don't care what the lab looks like.