I asked the same question to a Dell sales rep. Here is their answer: "I am very sorry for that, there was a Windows 11 Advanced that was planned by Microsoft but never was into production. Assuming it would be available, we did mention is as compatible on the specs sheet. Sorry again, I will escalate this to the concerned team and rectify it." Can't find anything about that on the internet. But I'll drop it - doesn't matter. 
Going through the XPS 8950 Setup and Specifications manual I see that the XPS 8950 comes with Windows 11 and Windows 11 Advanced. What is Windows 11 "Advanced"?
What is Windows 11 "Advanced"?