Label buffer doesn't work in map units

[bjpfei]

1.) open Layer Properties

2.) select labels

3.) mark display labels and select the field you like

4.) select buffer

5.) mark buffer labels

6.) select a buffer size and a buffer color

7.) If you now mark "size is in map units" there is no differenct to size in points. Seems that the size is always in points

[volter]

"New labeling" doesn't offer map units for the buffer at all. Is there a specific use case for it?