Spanish people from Latinamerica 

Some Mexican editors seem to consider that 9 to 15 million people in Mexico are ethnically Spanish. To support this they offer:
 a Tour operator page about tourism in Mexico: roughly as unreliable as it gets. But even worse...
 a link to the Encyclopaedia Britannica which simply does not have anything even remotely similar to the 9 to 15 million claim.

However, all that is not the real problem. The real problem is this: what have all those millions to be counted as ethnically Spanish? Note that we alrady had a discussion in About Regions with significant populations, where there was an agreement to erase the figures of Spanish people based exclusively on presumed ancestry and white race.

 If the reason to include someone as part of the Spanish people is simply ancestry, the amount for Mexico and other Latinamerican countries would probably get near 100% of the population... rather preposterous.
 If the reason are cultural traits, then we should know which are those traits, how they are different between individuals and what statistics we have about them.
 If the reason is whatever I can't think of, please enlighten me!
 I really would like to know if a conversation like this is common in Mexico:
 Hello, I'm Juan, I'm a Mexican of Spanish ethnicity.
 Hello, I'm Pedro, I'm a Spanish Mexican too!
 How nice, we have the same ethnicity, let's throw a celebration!