I'm sorry but you're just wrong. Armored forces was virtually non-existent in IJA, what armor they had was used as infantry support, their land based combat was based around en massed infantry shock attacks grinding into attrition warfare if swift victory wasn't achieved. Their extreme defense as you suggested was a product of late war ad-hoc desperation initative rather than a regular military doctrine.
You have funny double standarts complaining about issue of realism in regard of building defenses when Germans players can build bunkers or Pak 43s in 10 seconds. Same with your complaint about realism of tanks, when US factions has no heavy tanks, and allies need to call in even the most commonly produced Shermans/T34s.
You're really not helping your own argument by admitting the IJA was hugely inept when it came to armoured combat. And Ostheer have a buildable bunker, as do US Forces, but their entire faction designs aren't dependent on building fortresses. And yes the US Forces have no Heavy Tank, but they have decent Medium Tanks and Tank Destroyers. A Japanese Faction would be lacking both of these things. The British in CoH1 were a defensive faction, and everybody hated that. Remove the tanks (except Stuart and Tetrarch) and slap a Japanese flag on it though and suddenly it's in high demand? I don't understand the appeal.