"... sometimes sharing a copy with local law enforcement."... nope, it's ALWAYS sharing a copy and it is at a NATIONAL level. Why do you think the ratio of serious crime solving in Spain (and other European destinations) is higher than in many states in the US?
In any case, I knew of having to show your passport on arrival at hotels, guesthouses and rentals, but I didn't know about having to send it "in advance". Maybe something new? I am not in the loop anyway, sorry not to be able to confirm.
Btw, don't know if you misspelt but there is no "Ministry of Tourism of Malaga", in any case, government-wise at a local level in the city of Malaga, there is a "Consejeria de Turismo de Malaga". The Ministry is at a national level -much like your Secretariats in the US- and it refers to the country, not a city (=Ministerio de Turismo de España).