There's another wrinkle I didn't know about .name until someone else brought it up here. When you registered first.last.name you also got an e-mail forwarder for [email protected].
First off, it means selling doe.name separate from john.doe.name is literally impossible, because the e-mail forwarder only works if doe.name publishes the correct MX records. You cannot half-delegate a domain by record type, so .name can't shadow doe.name's MX record. So you're entirely correct that one of the two registrations gets denied because that's literally the only way the mail forwarder still works.
Second, it means hell for VeriSign's backend systems engineers. Along with the list separation you mentioned, any time someone registers first.last.name, it needs to also create a parallel registration for last.name, publish MX records on the corresponding subzone, and spin up a new mail server to forward mail for people who own a subdomain of last.name. I suspect this is part of why VeriSign wants to kill third-level domains more than anything else.
First off, it means selling doe.name separate from john.doe.name is literally impossible, because the e-mail forwarder only works if doe.name publishes the correct MX records. You cannot half-delegate a domain by record type, so .name can't shadow doe.name's MX record. So you're entirely correct that one of the two registrations gets denied because that's literally the only way the mail forwarder still works.
Second, it means hell for VeriSign's backend systems engineers. Along with the list separation you mentioned, any time someone registers first.last.name, it needs to also create a parallel registration for last.name, publish MX records on the corresponding subzone, and spin up a new mail server to forward mail for people who own a subdomain of last.name. I suspect this is part of why VeriSign wants to kill third-level domains more than anything else.