The reasoning is probably that one used www.subdomain and the other just uses a subdomain:
The Cloudflare universal certificates cover example.com and *.example.com.
This means that it covers any subdomain one level above the domain you signed up with. It will cover www.example.com and subdomain.example.com, as these are one level above the root domain, example.com. The certificate will not cover www.subdomain.example.com or a.b.example.com, however, as these subdomains are too deep.