What is the ruling regarding the share of spoils for someone who cannot typically receive a share (like an encourager of desertion or a boy) who fights using a rented horse?

Primary text

If the renter or the borrower (musta'ir) is someone who does not normally receive a share—either because they possess nothing (like one who encourages desertion or discourages fighting) or someone who is only given a gratuity (like a boy)—then the ruling on their share is the same as the ruling applied to their own horse.