Its important to note, Japan only has 3 Rank VI tanks as a whole, compared to those nations you are looking at who both have 10+, hence why their trees have more foddered content. The Japanese tree has far less to research already.
We don't do that for any nation at any rank.
Also worth pointing out, new Type 74 variants was a suggestion from Japanese tankers themselves just like Type 90(B).
To be clear, what was asked for is Type 74 variants to boost lineups. That's exactly what's coming here.
Foldering vehicles is not done on request, it's done by economical factors and development decisions when a tree is large enough to begin foldering things. Japan has 3 Rank VI tanks. Folders only start appearing when a rank is reaching its limits.
Naturally people are always going to want the quickest and easiest path to get something. But reaching the top of the Japanese tree is already possible in 1/3rd of the time of the US one. So you shouldn't expect to see many folders anytime soon.
Helicopters are a different class of vehicle type entirely and support ground forces.
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