I'm aware of who you are but I have no qualms saying that I can't take this as a valid reason. And the example of 11 domains... do you really think this would have any noticeable negative effect on the domain speculation problem? Like I said, they
already get those bulk prices. And 11 domains is a tiny number. The contrains are artifical yes, of course, what else could they be? There is no natural limitation here. I guess you ment arbitrary? It will always be arbitrary. Your suggestion to bundle it with a general Cloudflare plan is arbitrary just as well. There are many many ways you can try to lessen the problem. And I get it, bundling it with a budget plan makes sense though I'm not sure if one could 100% claim then that the domain registration is at cost-only. Then it's the same as any webhoster who bundles "free" domains into the mix.
The point of living up to the original promise: the original promise was to offer domain registrations at low prices. You are afraid to not live up to it? Well you don't because you don't allow registrations. You still have a landing page that advertises the service. You have call-to-actions called "register now" and the page [1] tells about new registrations and renewals. Then after clicking on it you land on a domain transfer page that doesn't really tell you that that's the only thing that works right now. So by being afraid to not live up to the promise you actually don't live up to it.
[1] https://www.cloudflare.com/products/registrar/