Why does supermaster have to be included in NS records?

[bugsse]

From the documentation:
"The set of NS records for the domain, as retrieved by the secondary from the autoprimary, must include the name that goes with the IP address in the supermasters table"
What is the reasoning behind this?

Scenario: I've built a dynamic dns service based on an API that lets users update their records. This API is hosted on a server that runs a local PowerDNS. The idea was to let this PowerDNS be a supermaster and push out new zones as they are created to a number of secondaries that are listed as NS for the zone. I do not want this master listed as NS in the zones since it primary purpose is just to run the API, not be a dns server.
The above mentioned requirement makes this impossible since the secondaries does not accept the zone unless the supermaster is listed among the NS records. I'm trying to wrap my head around why this is a requirement but cant figure it out. Should it not be enough to be listed as a supermaster, why does it also have to be a NS in the zone?

[Habbie]

"The set of NS records for the domain, as retrieved by the secondary from the autoprimary, must include the name that goes with the IP address in the supermasters table"

does not mean

unless the supermaster is listed among the NS records

it means -a- NS for the zone needs to be listed in the supermasters table, along with the IP of the supermaster. The listed NS does not need to be the supermaster itself. It can also be one of the secondaries.

The reasoning is that this allows you to reliably opt in to supermaster (autosecondary) processing for a zone, with more than just an IP match.