No. The VCRA only applies for Replica Imitation Firearms and not the parts themselves. Much like you don't need a UKARA or other form of valid defence to purchase say a MK16 handguard in black/tan or a defence to purchase a CTR stock.
I'm 99% sure it's a Japanese thing related to power. Pre-Ban = "High power", which is really more our regular power and then Post Ban is low power to comply with Japanese law.