They’re incredibly wrong, by a lot.
Insane → 8192 m × 8192 m → 67,108,864 m2
Large → 4096 m × 4096 m → 16,777,216 m2
Medium → 2048 m × 2048 m → 4,194,304 m2
Small → 1024 m × 1024 m → 1,048,576 m2
Tiny → 512 m × 512 m → 262,144 m2
Also, the sizes of the real life places is incorrect. For example, Cyprus’ actual size is 9,251,000,000 m2. This means the in-game version is ~0.0453389…% the size of the real life version.