Earlier quoted context omitted.
You need to dig the root nameservers these days, if you really want accurate glue record lookups. Don't trust whois.
Two different systems operating at different layers, though. I WHOIS the domain when I want to know which nameservers the registry thinks the domain should have. You can then dig in DNS to see what those nameservers are responding, but that's a separate level. (Note: I work in this field.)
For example, you cannot 'whois example.org', see DNS servers listed, and think "OK, those are the glue servers!". Nope. You need to dig at the root .org DNS servers, and find out what they have configured as glue records, and then query that.
$ dig +short org. NS
c0.org.afilias-nst.info.
d0.org.afilias-nst.org.
b0.org.afilias-nst.org.
a0.org.afilias-nst.info.
b2.org.afilias-nst.org.
a2.org.afilias-nst.info.
$ dig +norec @a0.org.afilias-nst.info. example.org. NS
;; AUTHORITY SECTION:
example.org. 3600 IN NS a.iana- servers.net.
example.org. 3600 IN NS b.iana-servers.net.
Now you know what the glue records are for a domain.Trusting whois, which is sporadically updated these days, and often inaccurate, won't necessarily help anything.
I get why you do trust it, it used to be reliable, it used to be accurate, it just isn't in many cases any more.
As for what the registrar thinks, I wouldn't trust whois for that, either. Not these days. I'd want to query the registrar directly, to find out.
(Maybe you meant all of this, but at least it's clear for others now, either way)