The mathematical joke here is absolutely brilliant! In the function f(x)=x, the output equals the input, meaning it grows at a constant rate (linear growth). But non-mathematicians, particularly media outlets, often misinterpret any upward trend as "exponential growth" - which would actually be something like f(x)=2ˣ where the rate of increase itself increases dramatically!
This is basically every mathematician's nightmare when watching the news: "COVID cases increased from 100 to 110... EXPONENTIAL GROWTH!!!" Meanwhile, actual mathematicians are screaming into their pillows because that's just... regular growth. It's the mathematical equivalent of calling a hamster a "miniature grizzly bear."