Paul, yes.. you are right as usual..

Arty in those numbers would be a real massacre in SPWAW terms. I'm not sure if they count in 50 mm mortars here as well, but i doubt it.. saw a similar one for the Finnish front with even greater number of tubes (including the 50 mm mortars).
About the tubes number listed here.. not all of these were used to support the first line attack, counter-artillery fire, disturbing fire, area firing to prevent reserves from coming through etc.
Your note about the arty takes me to my old wish of making OB/heavy artillery mission based (some never give up

.. you buy a number of missions from the OB battery instead of having it along all the time.. these missions should be more powerful and more expensive used for preparatory bombardments, especially tough spots etc-
Working more like air strikes than arty as it is now.
"If infantry is the Queen of the battlefield, artillery is her backbone", Jukka L. Mäkelä about the Finnish victory at Ihantala.