duh, it's part of the IEEE 754 standard. every language that handles floating point numbers has NaN handling, and in every language NaN is a float. the only reason this is brought up as a javascript thing all the time is that js doesn't have separate float and int types (aside from special structures like typed arrays and dataviews), it just defaults to float64 for simplicity and calls it number, which lines up with the "NaN is a number? nani???" joke.

you don't like it? consult the sorry excuse of thinking sand in the device you're reading this on, because this is etched straight into it. every FPU capable of handling float32 and float64 numbers knows what NaN is and handles it the exact same way.

this is one of the many things that sound unintuitive about programming but if you bother to understand the context you realise that if it wasn't this way, it would be way worse. one of the most important skills in our field is to understand computers for what they are, rather than be puzzled that they aren't what you thought they were, and it especially comes out in edge cases like this.