"A website/service cannot by definition be HA if it's reliant on one service or infrastructure provider." you seem to be conflating highly available with a diverse supply chain. A lot of highly available systems are "locked" in to one provider, whether it's broadcom/citrix/intel/etc.
Actually, yeah. How about worldwide nxos crashes due to the leap second bug? Or the various poison bgp updates that've made the rounds? Or overrunning an ospf domain? Anyways my point, if you read the sentance after my quote, was there's a distinction between sole source provider and "ha". Multi source supply is due diligence. But it's not a perquisite for or solution to high availability systems.
