> I doubt WFH will be impacted by this - not an insider but seems unlikely that the relevant people were on-site at data centers before COVID

I think the issue is less "were the right people in the data center" and more "we have no way to contact our co-workers once the internal infrastructure goes down". In non-wfh you physically walk to your co-workers desk and say "hey, fb messenger is down and we should chat, what's your number?". This proves that self-hosting your infra (1) is dangerous and (2) makes you susceptible to super-failures if comms goes down during WFH.

Major tech companies (GAFAM+) all self-host and use internal tools so they're all at risk of this sort of comms breakdown. I know I don't have any co-workers number (except one from WhatsApp which if I worked at FB wouldn't be useful now).