Ah, I know what it was. It was my birthday and I was camping in an area without reception. I've suspected for a while now that my reality's a simulation and so obviously none of you needed to be rendered that day.
Sorry if this causes any existential crisis' but you'll need to take that up with the Makers.
Might've been an outage in service or tracking, or denial of service, but seems far less likely.
Let's face it - developers just copy-pasted the same NPC to show how much creatures their simulation can handle, but didn't care to make them unique enough