Aren’t a lot of Hispanics part indigenous or part African? You can be “Hispanic” from the Dominican Republic or Cuba and be very African-appearing.
On the other hand, there are a lot of Spanish speakers from places like Brazil and Argentina who do not have any Spanish or Portuguese ancestry. They are Italian or Polish or German or Middle Eastern or something. (Like Carlos Slim of Mexico, and Pope Francis). They could easily put “caucasian” or “white”, even if they were born and raised in Latin America.
In our local area, we have a growing number of upper-middle class Brazilians. I don’t picture them caring to identify as “Hispanic”. They don’t need anybody’s charity.
It is true that many European-Spanish ancestry people who have been classed as Hispanic would want to identify as white. They are, after all, pretty much Caucasian.
But a lot of the illegal immigrants classed as Hispanic are indigenous people much like our American Indians.
It is logical that those who come from Cuba and Brazil would want to identify with their Spanish Caucasian or “white” identity to separate themselves from the indigenous Indians.
I live in Brazil. 1) We don’t speak Spanish down here, we speak Portuguese. 2) Many “whites” are actually racially mixed, as race in Brazil has more to do with literal color, rather than genetics. This is why, as is the case in my wife’s family, you can have siblings who are “Branco” or “Pardo.” 3)There are pure-blooded whites here, mostly descendants of late 19th/early 20th century immigrants from Italy, Germany, Portugal, Poland, etc., mostly in the south of the country.