Having lived in Melbourne, those are both pretty bizarre assertions, although it's a running gag for Melbourne that you can easily experience all four seasons in a day. In Australia, only coastal NT/FNQ qualify as tropical, with a subtropical slice from Brisbane down to Sydney:

https://plantmaps.com/koppen-climate-classification-map-aust...

I can't comment on the meaning of spring in Mexico City, but I assure you that it means plenty in Melbourne and its surrounds, colloquially and in actual weather. Even if we didn't get a lot of it this particularly wet year.

This is only correct if you round to the nearest billion people.

Around 250 million people live south of the Tropic of Capricorn: https://www.quora.com/What-proportion-of-the-worlds-populati...

That would be roughly the 5th most populous country in the world.

If we are making generalisations that big we might as well say that no one lives in the United States (population 330M, but rounded to the nearest billion it is zero right?)

I have literally never heard this, and I’m more aware of the vagaries of USA and European business and general practices than most others in Australia.

If someone on the internet says “Spring 2022”, I immediately assume it’s speaking of northern hemisphere temperate regions’ spring (because such dating is uncommon in the southern hemisphere to begin with and never used in public/worldwide internet situations because we’re more aware of these things), and after thinking carefully for a bit to straighten out in my mind when that actually is, I assume March–May 2022 or possibly a week earlier (equinoxes and such), because that’s what would be meant in Australia, if we ever expressed things like that (apart from the whole off-by-six months thing!). I would not expect June to be reckoned a part of it any more than I would expect March to be a part of Q2.

(Incidentally, a year or two back I heard suggestions that “Q2” may customarily be anchored to financial rather than calendar years in some places. Not sure if this is true.)

If by “spring” you meant to convey “the second quarter of the Gregorian calendar”, you failed to communicate accurately.

Not so. I would have guessed it was either Feb,Mar,Apr (astronomical) or Mar, Apr, May being the gardeners calendar. But Q2 is Q2. It's not just having to flip the season for the hemisphere.