How does a GSM signal get through a hole of about 1cm?

Question

Electronics

Greetings!
I don’t quite understand how a cellular signal can pass through a hole no larger than 1 cm in size?
After all, the wavelength of cellular and Internet communications is in the range from 5 to 15 cm. I
saw it here: https://www.youtube.com/watch?v=eOKXKbFYpwM&t=490s
reflected the corresponding wave?

Answer 1

And look at the microwave. Grid on the door with cells of 3 mm, but a wavelength of 2.4 GHz - 12 cm

Answer 2