You are right. As example, here is the 0°C isotherm altitude above the highest summits in the Alps shown by ICON-D2. And ECMWF with a coarser resolution displays quite the same map in Windy.
Freezing altitude (0°C altitude) at 3000m level seems inconsistent. At same location Airgram by same model displays the 0°C level at 850hPa (1500m asl approx.)
Is it a problem with the ICON-D2 ? It seems that the Meteociel app shows a similar map by the same model.
I could show a similar map from AROME 2.5km.