I am going to reply just by logic only.
The prayogas(ritual performance), are divided into two. Purva Prayoga and Apara prayoga. That is before and after ( apara- the other). Purva is for all that rituals performed for the benefit of the livin. Apara is for the dead soul and pitrus.
To distinguish between them , the difference are given.
And , to distinguish between Deva karma and Pitru karma the difference are given.
The tharpanams /Arghyams are given thru the different sectors( Theertham) of the palm.
The poonal is worn in opposite way for each.Probably the pitru loka and Devaloka may be -one clockwise and the other anticlockwise.
The parishejanams ( circling with water) are also done either clockwise or anticlockwise).
In normal advanced logical thinking in science also , there is a strong argument for existence of World and Antiworld. ( Galaxy and antigalaxy) Poistive and negative. For stability, the opposites should co-exist.
That is why every major religion has God and Devil .The Good and the Bad.
Both characters are distinguished by the actor in dress, facial expression, actions and behaviour, eating and drinking habits etc.
I expect explanations based on shastras aso in this regard.
Greetings