Thank you guys, I really appreciate the effort!
I looked back at my question and I think I didn’t make something clear or left it open to interpretation. Please allow me to elaborate and then comment on it myself first.
The mana indriya is located in the brain. The hadaya vatthu is located in the heart region. In one part, Lal mentioned that the mana indriya becomes manaytana and in another part that the hadaya vatthu becomes manayata.
Before reflection, the sañña I had of manayatana was to automatically connect it to the mana indriya that is now being used as an ayatana, not the hadaya vatthu. Let’s say, sort of like a “6th passada rupa.” (I don’t have any confusion about the fact that an Arahant doesn’t have ayatana, and that ayatana can only ever come into being due to “san”)
However, it makes sense that we have a mana indriya only when we’re in a human body. The moment the manomayakaya comes out of the body, whether during an NDE, OBE, or at the death of the physical body, that manayatana can only refer to the hadaya vatthu from where the mind arises. Same goes for devas and brahmas. As long as we have a human body, they seem separate in a way but they’re part of the same system.
So the basis of my question was due to having an incomplete understanding of mayatana/mana indriya.
Although I thought A got answered to my satisfaction, it didn’t really. This became clear after the subsequent comments. Thank you for giving the extra push to let me think critically. I’m sorry for the confusion.