There's no way these RCS numbers are right. No way bird is 0.01 m^2 = 10 cm by 10 cm of flat metal.

[Yongpeng Sun-Tastaufen]

These numbers look bogus to me. https://www.globalsecurity.org/military/world/stealth-aircraft-rcs.htm

F-15 is definitely not 25 m^2 = 5 meters by 5 meters of flat metal. F-15 is only 19 meters long. In the front it should be equivalent to about 3 m^2 = 1.8 meters by 1.8 meters of flat metal, because it's not flat in the front and it ain't that big in the front. The pilot's body is only about 0.5 meters wide. F-15 front is only about 2 meters wide in the nose and cockpit main section. The wings and tails have very small area.

 

[Fawadqasim1]

Wow

 

[Yongpeng Sun-Tastaufen]

Wow

I would say F-15 Su-27 both 3 m^2, F-22 about 0.8 m^2 and F-35 at 0.4 m^2.