Unfortunately, that's a trivial signal to emulate.
At a minimum, you'd have to validate them by confirming existence in the Wayback Machine.
Otherwise agreed that those are indeed high-signal documents. Increasing reliance on integrated educational software means that even such things as online syllabi are increasingly rare.
The type of sites GP is talking about are typically hosted on .edu servers, under faculty webhosting (often featuring a "/~profname/" in the url). That's a non-trivial signal.
Pages at extant domains might variously be available to undergraduate or graduate students, faculty, staff, and adjuncts. Those might either directly host emulative material or be convinced or compromised into hosting content.
If there's one thing that the Internet's history to date has proved, its that perverse incentives lead to perverse consequences.
At a minimum, you'd have to validate them by confirming existence in the Wayback Machine.
Otherwise agreed that those are indeed high-signal documents. Increasing reliance on integrated educational software means that even such things as online syllabi are increasingly rare.