Given that, I see these possible outcomes
- the client's admin might not care about this site at all (effort to hide stuff would be wasted?)
- the client's admin might consider content 'unsafe' that seems fine/okay to the site operator => Blocklist, failed to archive what you suggest
- the client's admin might consider content 'safe' that the site now refuses to share => Curse site and Mozilla, switch browsers and/or consider that site broken and the operators morons (similar to 'breaks zoom on mobile devices' today, for example)