Based on traditional practice of Sishta BrAhmaNAs, for Yajur Veda Apastamba sUtra, only KANda Rishi TarpaNam is prescribed. There is no Pitru TarpaNam as part of the upAkarma ritual.
The upAkarma practices vary in the case of other sUtras . Each one should follow his own sUtra.
For RG Veda and SAma Veda, Pitru TarpaNam is there as part of upAkarma ritual.
There are variations in the sUtras. Hence we have to follow what is ordained in our own sUtra after properly learning the same from a Guru.
There are variations in the sUtras. Hence we have to follow what is ordained in our own sUtra after properly learning the same from a Guru.