And it won't be removed.
Having your NS reachable over IPv6 is important, especially for IPv6 only networks to have the ability to query for your domain if they ever choose to send packets your way. And yes they exist, in lab & in production, and pretty soon (2-3yrs) mostly in production in regions that can not longer get IPv4 resources. Also the test is more about testing if you (meaning all of you taking the test) figured out how to run DNS software and make it reachable over IPv6 & serve IPv6 records. Not so much the relying on someone else to think for you. These are technical tests aimed at people that want to learn and test what they've learned. Large companies in fact DO operate their own nameservers, please WHOIS entities like Google, Microsoft, Yahoo, GE, etc. (hey, you said large companies).
Fact of the matter is even if you skipped Guru, with your current "in the top 3" registrar you wouldn't pass Sage if they won't create AAAA records for their NS and push them into the TLD servers as glue. If companies & individuals aren't pressing for IPv6 support with their registrars, then of course they won't see a reason to provide for it. Don't be defeatist! Tell them you want the support, if you have friends/partner companies using them and interested in IPv6, make them tell them! Vote with your money, regardless of that registrar's status, anyone can sell you domain registration. Also I cannot think of a single registrar that doesn't let you run your own name servers and forces you to use theirs. If you run your own name servers, and they even let you create host records in your domain for them, AND even let you enter an IPv6 address for that host record, then they should be capable of sending it up to the TLD servers and providing glue.
You are also always welcome to reset certification and use a different domain that will have full IPv6 support all the way to the TLD servers. Simply email ipv6@he.net regarding this and we'll process the request.