How come, when utilizing a CDN, some hosting providers require to point nameservers to those of the CDN and some don't?

Question

When I had an IaaS modeled hosting environment I wanted to utilize a CDN (CloudFlare) and I was required by the hosting company staff to point the name servers in my domain registrar to those of CloudFlare (instead to those of the hosting provider).

When I had a PaaS modeled hosting environment I wanted to utilize a CDN (CloudFlare) and I was not required by the hosting company staff to point the name servers in my domain registrar to those of CloudFlare.
Rather I was told that just enabling the CloudFlare option and configuring it correctly would be enough. I did so and went to the CloudFlare diagnostic center and there I found an error about nameservers.

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I have inquired the PaaS modeled hosting provider's staff why the aforementioned error isn't a problem and a staff member replied something like:

We are direct partners with Cloudflare and we have made it possible to use Cloudflare with only two records that are updated on our end which are Cname and WWW.

I believe the staff member was wrong in thinking the WWW redirects are by themselves a Cname DNS record but here I just seek to learn why in the IaaS scenario I had to change nameservers and in the PaaS scenario I didn't have to and the staff member's reply didn't really explained that at all.

Answer 1

The support person is right that you don't need to point your nameservers to Cloudflare. Last time I looked, it was only for Enterprise plans, but now it also mentions certified hosting partners in the FAQ about using / not using Cloudflare nameservers. It's also very possible that the diagnostic center is giving false alarms for such a setup because in most cases people do need to point nameservers to Cloudflare.

Support may be mistaken in thinking they've set it up properly in your case (not as automatic as they thought?) or your host may think it's your responsibility to get it working. Do they have any FAQs, docs, anything that explains how their relationship with Cloudflare changes things on your end?

There are a few types of partnerships that Cloudflare has with hosts. It could be that your host peers with Cloudflare in this program but I think most details are walled off from anyone below Enterprise.

So, I think you should simply ask the PaaS host: What type of partnership do you have with Cloudflare and how does this affect me and my DNS / nameserver issues? Where can I find information on the steps to take to fix this myself? Or if it's managed hosting, they should get it working for you.