That's a good argument against using your technical contact e-mail address being at a different domain, which is a recommended practice, but it doesn't make any sense where nameservers are concerned. DNS servers use IP addresses, not hostnames; otherwise you'd have a chicken/egg situation if you tried to look up information about example.org using ns1.example.org.
Actually, I'm not even sure what situation you're trying to describe. An entire zone file going missing? Your names won't resolve then regardless of what nameservers your domain is using.
Suffice it to say, there's no reason to not use nameservers that have names in the domain you're using them for, if the DNS servers in question are actually under your control. I would recommend against doing this sort of fake DNS server thing, but for different reasons.
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