With yellows it is all about the color.
A lot of the time the tone and shade of lab yellows is d8fferent than mined diamonds of the same grade.
Even with mined you can have 2 stones with the same grade very different looks.
Have pics or vids? Seen them in person?
When it comes to yellow lab diamonds, IGI is virtually useless. I don’t blame them, as fancy color diamond grading is a completely different animal than colorless diamond grading. They’re just not set up to do it properly.
To add insult to injury many of the pictures posted online have been messed with to change the color. To say nothing of the fact that as has been pointed out someone sent you the same picture twice