I don't know the technical term for this precise part of the car, here's an image.

This is a newer model, but on the BYD seal I examined I nearly bent this just by leaning on it. Completely gave way under me, as it's just a thin piece of floating metal with a small rectangle of foam under it.

On a more traditional manufacturers car body this would be part of the unibody - directly joined to the frame. On BYD it's a floating panel. Same with the side panels, so if you open the door you can see between the car panel and the interior car frame. There is a thin piece of foam insert to block access, but it was loose and easily came out - more premium manufacturers make this a part of the unibody again. It prevents water (or debris/dirt) coming in between the panels, and strengthens the body, at the cost of some weight due to the added steel. BYD - nah, foam insert is fine.

Like I said, they're built to a price point and there are many points of failure that other manufacturers have learnt are not corners worth cutting.