The quote says that it was the PowerPC core (PPE) was all that was used in the Xbox 360 processor and all that the PPE is is an implementation of IBM's Power IS

The quote says that it was the PowerPC core (PPE) was all that was used in the Xbox 360 processor and all that the PPE is is an implementation of IBM's Power ISA, one of several (see https://en.wikipedia.org/wiki/Power_Architecture#Specifications https://en.wikipedia.org/wiki/Power_Architecture#Specificati... under Power ISA v.2.03). It's no different than an ARM processor vendor re-using a core design for multiple customers. The thing that made the Cell what it was, namely the 7 SPE units, were not used in the Xbox 360.