I think Nielsen caveats the point this article is making in the first five seconds of the video: “I like to say that designers are not users, except of course if you’re designing a product for designers, but that’s a rare exception.” Maybe panties can be un-bunched based on this :)
I definitely agree that a designer’s intuition about how they themselves would use a design is a powerful tool and is not to be ignored. However, I’m designing interfaces for audiences of millions that I would personally never use had I not designed them. As a designer, to actually be a user of an enterprise product you’re designing is a luxury and likely an edge case. Should all designers only work on projects they themselves use? That would be a pretty serious devaluation of design as a profession. Should all mechanics only work on cars they plan to drive? A great mechanic also employs skill and even art in the service of things that other people use.
A motivated and skilled designer isn’t hamstrung if they aren’t a user of the system. Is there a designer worth their salt that would take on a design project and resolve not to gain comprehensive knowledge about the thing they are designing, even if they aren’t a user of the design themselves?
In these scenarios, I think a better plan ensures that personal intuition, skill, and experience are brought to bear when designing, and to ensure that actual users of the product are approached through research and testing to validate and course correct.