According to the texts, khandārinibbana is the end of the world.
When you say only body remains and not the mind. This is certainly not an end of the world you are describing.
This word ‘body’ of which you speak, can not be pinned down as true & real, it is a convention used in as far as the aggregates are present.
So when you say ‘there remains a body’ you are essentially saying ‘there khandas are present’.
And so you have to take note of this because if in describing khandāparinibbana you say that the body remains.
You are essentially describing khandā after khandāparinibbāna, you are not describing the khandaparinibbana.
In other words, you are describing a world after the end of the world in asserting that the end of the world occured in the world wherein the body remains.