Thank you for another post:
“Nāmarūpa Paccayā Salāyatana”
You have explained to us the difference with phassa and sanphassa — something with “san” vs something without “san“.
I wonder if we can think along the same way here: there is no “san” in indriya, but “san” is involved in ayatana.
However, if this is the case, then I remember reading about nibbana some time ago, in a post where nibbana was referred to as tadayatana. I wonder why ayatana was used there in the context of nibbana; “tadayatana” sounds like a contradiction in terms.
Best,
Lang