I think that all those figures prove is that HN has a Bay Area bias, not that "the Bay Area is utterly exceptional in terms of tech/startup career opportunities".
I mean, it is great, but a developer would have no problems finding a good job in New York or Boston, at least.
Another possible interpretation of the jobs/population number is "which cities have lots of job openings despite not being dominated by the tech industry," if someone wanted to be somewhere more diverse. Though, unsurprisingly, the answer is basically "the big ones" so it's not all that interesting there.
My aim in posting these figures was just to give an example how correlating the number of job postings with each area's population can give additional meaning to the data. So instead of being fooled by a population graph masquerading as a job graph, we can see where jobs outpace the population, and by how much.
For a more detailed analysis, marshaling job postings from additional startup-focused job boards and correcting the city population figures to reflect the metro areas would provide a minimum level of rigor to the data. Comparisons between startup job postings and 'corporate' postings could provide a bit of extra perspective as well.
I mean, it is great, but a developer would have no problems finding a good job in New York or Boston, at least.