I've asked chatGPT a fair number of Fortran questions. There are differences - Fortran is still in use lots of places, there are forums and documentation sites (though presumably that's true for COBOL). But compare to python, there is way less info out there on how to do different things, for example little Stack Overflow content.

I'd say I has mixed results, definitely chatGPT knows the language and can give examples but I've also had a lot of frustrating things it wasn't able to resolve.