Rust in boot?

[TomWM]

Just joined to post my pics to help the community solve the rust vs no-rust stain puzzle.
Not a Yaris but the same problem. RAV4 owners might be less sensitive to issues like this but both the Ravs I've owned had this.

In both cases it's at the lowest point of the boot. They have different boots with the lowest points in different places.

First I thought something was spilt by the prev owner that caused the rust or the other way around - it started rusting and was treated with some magic liquid.

Then I started looking it up online and I found pictures about the spare wheel in which the stain was visible in the exact same place which suggested it is a manufacturing defect. Which was further proven when I found a similar stain and bubbles in my brand new phev. 

So the pictures
My 2019 Rav4 self charging hybrid (red) - looks like it's rust bubbles in the middle of the stain
My 23 Rav4 PHEV (white) - it's less obviously rust

Might not be rust but definitely not anything you can rub off. The paint is so thin on non-visible areas that it disappears if you firmly touch it let alone rubbing it. The whole bottom panel is so thin that I could easily rub a hole in it or make the whole back of the car vanish.

What do you think?

[FROSTYBALLS]

Split from topic in Yaris/Yaris Cross forum.