The Sun & the Moon are about the same apparent size, but they are not the same size. They only appear the same size because the Sun is 400× larger and also 400× farther away. To illustrate this, we can use forced perspective in photos.
Flat-Earthers insist that the Sun & Moon are the exact sizes just because they appear the same size. By the same ‘logic,’ we can say the girl above is the same size as the Eiffel Tower.
This girl is not as tall as the Eiffel Tower. She appears about the same height because she is much closer. Even if she is smaller than the Eiffel Tower, she can block the Eiffel tower from view. Not unlike how the Moon can block the Sun during an eclipse, despite the Moon being much smaller.
To determine her actual height, we have to look for other information. Her apparent height alone is not sufficient to measure her height. In the same way, we cannot say the Moon is the same size as the Sun just because both appear the same size in the sky.