Correct. SLAs aren't calculated off status pages, there are far better ways of calculating it (running a query over responses, for example). Most modern SLAs are customer initiated anyways, so the customer is writing in to request this rather than automatically calculating them. The status page doesn't need to show anything for a customer to provide logs indicating a QoS less than that promised in the SLA.

I don't think it's politics (maybe AWS's is, but GCP wasn't IMO), it's really a function of "in large scale software systems things are constantly failing in all sorts of ways, and it's really hard to output a meaningful automated signal that things are broken. Sure you can set up pingdom type health checks on every endpoint, but even then you're not necessarily guaranteeing that things are working properly.

Source: worked at a few cloud providers, paid out a few SLA violations