I know of a site where all the data is embedded inline ("var Person = {firstName: 'Fred', lastName: 'Smith' }") then rendered to HTML with JS. No endpoints, Javascript not JSON, complete pain in the ass to extract without rendering in a headless browser first.
Isn't this better? Why do you need it render when they're giving you basically JSON of the data (might need to quote the keys in strict parsers), just extract that.
The short answer is that, yes, the only parser available to me is that strict. If I'm going to jump languages, I might as well go the whole hog and jump to Puppeteer.