sets started to produce different number of output files

I am not sure the following change was intentional or not. Some of my VV cases started to break down at the level of plot production, hence realised the following behaviour change.

Minimal test case: sample-issue.zip - to reproduce the issue, just execute Allrun and inspect postProcessing content for different HEADs.

The following system/sample file yields different number of output files for v2112 (14aeaf8d) vs dev (d7c87390) for the minimal test case:

type                sets;                                                       
libs                (sampling);                                                 
fields                                                                          
(                                                                               
    U                                                                           
    turbulenceProperties:k                                                      
    turbulenceProperties:R                                                      
);
...

For v2112 (14aeaf8d) or for the develop at least six weeks ago (1a55829e), three files were produced:

y_turbulenceProperties:k.xy
y_turbulenceProperties:R.xy
y_U.xy

For dev (d7c87390), a single file was produced:

y_turbulenceProperties:k_U_turbulenceProperties:R.xy

Could you tell me if this output change is intentional or not? @andy @mark @Prashant