Is there a reason to believe this would skew results?

i.e. Are you assuming (insinuating) jobs for some programming languages are more likely to be fake

I would assume so. I expect there to be a lot of job postings looking for more "sexy" technologies to create the visage that those companies are growing and planning towards the future. And conversely I wouldn't expect any job postings of old "streets behind" technologies like COBOL to be fake, as they wouldn't help with such signalling.