One billion and Un billón

In Spanish "un billón" is not the same than in English "one billion", in Spanish it is 10¹² (12 zeros = un mllón de millones) and in English it is (10⁹) (9 zeros = a thousand millions). According to this video by Dr James Grime and Dr Tony Padilla, the Spanish way is mathematically more logical.

But in Spanish, the logic in that is not just mathematical, but also linguistic (and not just etymological as shown in the video): "un millón" (10⁶) and "un billón" (10¹²) are not numeral determiners, but nouns; so we say "mil cosas" ("mil" is a numeral determiner -a.k.a. numeral adjective) but "un millón DE cosas" and "un billón DE cosas". There is no need to have a word for a number that can already be expressed with a rather simple expression as "mil millones"; just when the last numeral determiner possible is used (999,999 = novecientos noventa y nueve mil novecientos noventa y nueve is STILL a determiner), then we need another noun to avoid a complex expression as "un millón DE millones DE cosas".

PS: Escribí este post en inglés porque en un principio era un comentario para el video mismo, que está en inglés. Pero quedó muy largo y me gustó, así que decidí publicarlo acá.