[QGIS-Developer] Aggregate (GUI) - Load fields from layer

[pathmapper]

Hi,

the processing tool "Aggregate"

https://docs.qgis.org/testing/en/docs/user_manual/processing_algs/qgis/vectorgeometry.html#aggregate

offers to "Load fields from layer" which according to the docs has the 
purpose "You can load fields from another layer and use them for the 
aggregation".

Is this supposed to use then also the values from another layer?

Asking because it currently only loads the field name/type but doesn't 
use the values.

Cheers,
Björn