The root servers don't have the glue record for every domain name though. All they have is the glue records for the TLDs. (which is in the zone file you linked)
Every time I stand up new name servers I have to add the glue records into the root servers or the name servers do not exist. In fairness to me I keep forgetting the trend is to shove everything into big centralized DNS servers as it is something I would never do at least not as a primary.
Afaik, those glue records are held at your TLD's registry and served by the tld nameservers, not the root servers.
It might be nice to get a zone transfer for every tld, but that's not possible for the public. (I understand there's some way to get many of them, but $$$$)
I run my own name servers. I never use the name servers of a registry. I can see the glue records of my name servers in the root servers. In fact the reason I left NetworkSolutions (web.com) was that their interface to update the root servers broke and there was nobody left that knew how to fix it. I'm sure they must have fixed it by now but I was being impatient only waiting 3 weeks.
I should add that I have been adding name servers to the root servers since 1998. I've just never managed one of the root servers and I guess nobody on HN has either.
Im not confused at all. For your recursive servers to know how to get the name servers they have to have a hints file, that tells them what to use for the tld, then from the group of root servers associated with that TLD you get the glue (name servers) assocociated with the domain, then you query the authoritative name servers for that domains resources you were requesting. Every name server has a glue record in the root servers. I can manually walk you through it with dig if you would like.
I need to clean up the formatting a bit but this is a walk through. [1] I think I know where your confusion is but I will wait for your reply.