I don’t like those words when someone asks when do you expect x to be released. I still cannot imagine any modern business using “when it’s done” I still haven’t been show an example of a business using them except the john carmack quote from 10 years ago.
I'm not sure I understand any subtlety you might be expressing. I can't imagine a modern business that doesn't use this approach in some way for some services, typically when we start talking about teams that deliver services to _internal_ customers.
Perhaps you'll consider these:
(1) "Best effort clauses" are often found in contracts where somebody providing a service cannot be specific, including being specific about a delivery deadline. These contracts are common in many industries. You can read up on those clauses and get numerous examples.
(2) My current employer (Ohio University) has an IT department where "best effort" is all they promise for certain services they offer to departments. Basically, take a number and they'll get to you when they can. The service level agreements state as much.
(3) Internal project teams that work on projects with an iterative approach that focus on features, not deadlines, are quite common. They have internal customers. Easily the majority of project done by my employer's custom application development team are of this type. Sure, they also do project with deadlines, but that's usually when the project is being driven by a business need to hit a certain date. Not all projects have that need.
(4) I've worked in a couple of places where "when it's done" is effectively the working arrangement. For example, I was a contractor at a US West (a "Baby Bell" phone company) that published Yellow Pages. Internal developers to a legacy system were gone and the company wanted to add new features. When could I have the features ready? No idea. I'd never seen the system before. We developed a feature, tested it, released it, and then the sales people started selling ads using the feature. Of course the sales people wanted to start selling ads with the new feature once they knew we were working on it. Management wisely knew to forbid that. Management didn't want to promise something to a customer, make a sale, and then be unable to deliver. We worked that way the entire time, even after I was able to make reasonable estimates. Management never wanted to risk being in a situation where they would make a sale and then be unable to deliver.
I see TFP's approach being consistent with all of those. "When it's done." You can interpret it as being said with arrogance or stubbornness, but I really just think they're using it a a concise expression of their philosophy.