I believe that world-space canvas no longer gives a damn about Dynamic Pixels Per Unit or Reference Pixels Per Unit when rendering Text UI in the world space.
The density of texture changes, BUT text size is determined by world space. 1 point = 1 meter. And you can’t enter fractions there.
Now, I could probably manually rescale my canvases with that in mind, but is there a sort of workaround (to get old behavior) or should I file that as a bug?
On the screen you can see text with size of 1 on unscaled world space canvas with DynamicPixelsPerUnit and ReferencePixelsPerUnit set to 100. The cube is 1 unit big.
My solution:
Set the canvas size to a large one (800x600 etc) and scale down the whole canvas to a proper look instead of setting the Dynamic Pixels Per Unit to some huge value.