Hosting the own website on a different network is ok.
But they have a distributed DNS anycast network - and don't trust it enough to host their own domain?
When/if something breaks, it could in spectacular fashion. I'd expect them to use themselves as primary nameservers with other companies as secondary just in case.
It's suspect, but same can be said about any hosting company outsourcing their main sales site.
I think fine in downtime to hose your own sales site
But support, well that better work. Outsource that.