By design, only one rack ATS can be connected (powered) to a pair of rack PDUs in a rack. It is mainly because of the predicted power, power sold, and estimated load strategies, which treat primary and secondary rack PDUs as if they were paired. One rack PDU cannot be paired multiple times.
A possible work around is to model one rack ATS with the combined sum of the outlets of all the other ATSs. Add the other ATSs as "dummy" ATSs, that is, without connecting any equipment to them. This way the inventory reports will be valid.