They may not have realized that no one can read it. ScienceDirect silently lets you past the paywall if you arrive from Google Scholar. I imagine that HN strips query parameters, and even if it doesn't, the token is only usable by one person.

You can access the full HTML by clicking the link here: https://scholar.google.com/scholar?hl=en&as_sdt=0%2C45&q=Sex...

Edit: this only works if you're logged in to a Google account.