São Paulo is a much more globalized city than Rio, which is really navel-gazing. (Most families in Rio can trace their ancestry centuries back, while São Paulo is usually the largest $(nationality-descent) population outside $(homecountry). This makes for cultural differences.)
But: it's not like carioca customs bleed over to the workplace any more than, say, West Texan customs do. I mean, at my workplace we wear suits but not ties; whenever in São Paulo we tie up. That's most of it.
Is 'almost everyone you met' a representative sample of the population of SP? Of Brazil?
To say that Brazilians are late is a generalisation. To say they are on time is also a generalisation.
Also, the article summary you cited says nothing about punctuallity. It talks about pace of life. Where can I see the full study?