I am pretty sure Heroku has a Linode box or something for their status page. I may be wrong though. They may also have moved it but that would seem like an incredibly dumb idea.

I worked there and I vaguely remember something like this but it's been a long time.

If I had to guess this is probably a DNS issue (it's always DNS).

I agree with your lead statement and argued as such, but was overruled. Last I knew and understood, Heroku Status is static pages pushed out to Fastly, with the internal admin site (that does that work) running in a Heroku Private Space. If you look at the DNS, it still appears to be served by Fastly, and Heroku Private Spaces are generally pretty isolated infra, so I would be curious what the failure mode was here. But ultimately this is the fire you play with when you self-host your status site...