> when that page disappears after an acquisition or rebrand.

Sadly, it does not even have to be an acquisition or rebrand. For most companies, a simple "website redo", even if the brand remains unchanged, will change up all the URL's such that any prior recorded ones return "not found". Granted, if the identical attestation is simply at a new url, someone could potentially find that new url and update the "policy" -- but that's also an extra effort that the insurance company can avoid by requiring screen shots or PDF exports.

It sounds like you work at Microsoft, they do that ALL the time.