

I think the unwillingness to switch Ukraine to 155mm caliber prior to 2022 has less to do with the west trying to not provoke russia and more with Ukraine’s desire to use existing stocks and tooling in domestic ammo factories. They themselves ordered DANA M2 in 152mm caliber in 2020. Only after the invasion they realized they will need much more ammo then they can produce domestically and west started providing 155mm systems. Already in 2022 Ukraine has been given German PzH 2000, Slovak Zuzana 2, French Caesar and eventually Swedish Archer. The ammo problem simply took time to solve, but it seems European productions is ramping up and the Czech initiative is still ongoing.
The need for armoured cabin is now well understood and I would say that Swedish and Czech solutions go even further with autoloaders and targeting computers reducing the crew needed to as little as 2 and removing the need for the crew to leave the cabin during a fire mission.
This statistic alone doesn’t tell you anything because according to a Land forces production overview table here:
https://en.wikipedia.org/wiki/Military_production_during_World_War_II
USSR had Germany beaten in artillery pieces production 5:1.