They are speaking English so a billion is a thousand million. There is no English speaking country anymore that uses long scale. So no English speaking country uses miljard for a thousand million.

So for context, in English billion is thousand millions, but in Spanish is a million millions (so, an English trillion)

They gave using the English definition.

It's slightly more complicated than that and in the case of most natively English-speaking countries you'd be wrong, so I'd argue that in terms of the English language you're wrong

So in most of western Europe and most of South America, you'd be right as they use the long scale, but none of those are natively English-speaking nations. UK and Ireland use the short scale, as does the US, NZ, AU. Canada uses both, I'd assume the French speaking part uses long scale. Eastern Europe, Northern Africa, the Gulf states, and NW Asia actually use short scale with milliard instead of billion, and as you go towards south or east in Asia, you'll run into completely different number systems, such as the funky Indian one that goes by hundreds rather than thousands as groups starting with 1,00,000 (1 lakh) and 1,00,00,000 (1 crore).

TL;DR: There's no unified worldwide standard, but for pretty much all English language usage, you'd be wrong.

No