When is the nano-texture glass Pro Display XDR better than the standard one?
You kinda got it all... that's it. It's just an improved matte display that minimizes reflections and glare, at the cost of some saturation and crispness. The only difference is how the matte effect is done: in a standard matte display, it's a coating, while on the Pro Display XDR, it's etched into the glass.

In a professional environment, the requirements are really the same as a non-professional one: while the glossy version is better if you can work in a controlled lighting environment, that privilege isn't always available (such as on-location shoots), and the benefits of the matte display can outweigh the downsides. It really does just depend on preference and working environment.