It doesn't seem to be using the Javascript. Looking at the page source, it has already made the determination before the Javascript runs. If I load the page so

It doesn't seem to be using the Javascript. Looking at the page source, it has already made the determination before the Javascript runs. If I load the page source in Chrome, it already includes the "You are not Chrome headless" message, but when I run it in a scraper I maintain, the page source loads with the "You are Chrome headless" message, even without running any Javascript.