Same for France and Spain, which is what I am familiar with. I am expecting it to be true all around.

The map of France shows maybe 100 castles? If you include castles, forts and chateaux (which it seems the map aims to do) France has around 45000 of them, including 15k medieval castles (military), an other 15k from the Renaissance period (mix of military and luxury), and 20k more recent ones (some military, many luxury type).

I know if at least 20 medieval castles within 1h of my hometown and not a single one is here.

For Spain maybe 10k to 20k castles and forts. Out of which at least 2500 genuine medieval castles (not just big houses with fortifications)

Missing all of the "moorish" forts in Andalusia...