You aren't allowed to have a CNAME on the naked domain - it has to be an A record. It's not a shortcoming of the host. You'll have to make an A record that points to the same IP as www.
That's not true. The domain name system doesn't really know about different levels of domains, so such a rule doesn't even make that much sense.
What you are not allowed to have is a CNAME record in addition to anything else. So if you want a TXT or SRV or MX record, you can't also have the CNAME. Makes sense as the latter basically means "look here instead".
While you're technically correct that the specification doesn't specifically say that you can't have a CNAME on the root domain, it is still true that you cannot have a CNAME on the root domain because DNS requires that you have SOA and NS records on the root domain, which means that a CNAME is not possible due to the rule you cite.
What you are not allowed to have is a CNAME record in addition to anything else. So if you want a TXT or SRV or MX record, you can't also have the CNAME. Makes sense as the latter basically means "look here instead".