I think they mean that Common Lisp has bigints by default

As do Scheme and most other Lisps I'm familiar with, and integers/floats are typically specified to be distinct. I think we'd all be better off if that were true of JSON as well.

I'd be happy to use s-expressions instead :) Though to GP's point, I suppose we might then end up with JS s-expression parsers that still treat ints and floats interchangeably.