I'm sorry I have never seen a katana with a blood groove, or fuller so I assumed.
I am aware that groves are not created to release pressure when you stab some , but to make the sword light weight.
I could debate that katanas are complex, but I haven't studied other swords so I have nothing to compare with. I came here to learn, forgive my ignorance.
I have only studied the modern katana, not the older forms of the weapon.