I believe this is a New Yorker magazine house style thing. I'd assume the author uses numerals in the book this article is based on.

If there are two options, you can trust they'll go for the more verbose one.

Autors are often paid by word count. Note that I'm not saying that's the reason here, but it could be.

Also Cape Town is a city in South Africa..no idea where Capetown is

It's near Stellen Bosch

That's simply good writing practice. I find it more taxing to read digits than prose.

I was taught numbers up to ten should be spelled, the rest use digits

Chicago Manual of Style (though it says 1 to 100, er, I mean one to one-hundred). I try to use a CMOS subset for my professional/technical writing, mostly for consistency, but, partly so that I don't need to argue with people with subjective opinions about how I'm writing it wrong.

Thank you. To me after reading the parent comment the numbers option was so evidently better that I didn't even consider that someone like you could exist. My conception of humanity has been slightly enlarged.

If I may ask: Do you also find numbers more difficult to parse when doing math pure math operations? Is this:

Two hundred thirty five plus one thousand eight hundred twenty two

Also easier for you to parse than this?

235 + 1822

Or do you have two "parsing modes" ("text" and "math"), and going from one to the other is the difficult part?