"Microsoft's the 800-pound gorilla and as NT 4.0 finally slouches off into the sunset, the upgrade path from NT domains seems to point to AD.'
Then you would be incorrect in your assumptions as much as the author of the "article" was in his technical review of directory services.
As someone who has migrated from Windows NT Domain system to Windows 2000, I can tell you that the NT world may be moving (albeit, slowly) to Windows 200x, it is most certainly not making the transition from the NT Domain model to ActiveDirectory at the same rate. AD still lags a great deal behind in the migration path and many Windows-shops are still using the NT Domain model instead.
Part of your perception that is flawed is that Windows 2000 requires AD. This is far from the truth. Indeed, Windows 2000 will happily function using a Windows NT Server as a Primary Domain Controller and that Windows 2000 server will be content as a member server within that NT Domain.
In other words, just because you have Microsoft's latest server OS does not automatically mean you must use Microsoft "directory" service to run it.
"Whether that's fair or right is not a question I want to answer."
Then you should not have made the statement if you are not willing (or more rightly so, incapable) to back it up.