Wrong size for label

[aperi2007]

In the new plugin (perhaps also in the old plugin) the label size seem wrong (too big).

The image show the case:

The BLACK label if from a local vector layer .
The BLUE label is from a WMS layer return for a mapserver and a service exported from the same qgis project.
The size of the BLUE label is too big.

This don't seem a bug but instead a different kind of measure for the label size.
So perhaps the only solution is to apply a fixed reducing factor.