While your interpretation could be correct I took that to mean future versions like A14Z (or whatever they call it) A15Z and so forth, not that they will have a family of different Mac SoCs in every A* generation. There might be differences in the same way the A12X and A12Z are "different" so they can re-use the same die with 8 big cores across a lot of stuff by disabling cores in lower end models. They might start binning so they'll have different frequencies to give higher end machines higher clock rates instead of having to select a lower bound frequency that almost every chip can meet as with the iPhone.
They might want a second die for the bigger machines since they would need a fabric to connect multiple chips like AMD (doing a monolithic huge die like Intel just doesn't make sense to me so I discount that as a possibility) though they certainly could do a single die for all Macs that includes the fabric which remains inactive in single chip Macs. It isn't like the fabric would impact die size much in today's processes (it is probably more costly in pad area than transistor area) so considering the ever escalating cost of mask sets it might be cheaper to have unused fabric on all chips rather than do two separate designs and require a second mask set.
On the other hand even though a second mask set costs more, if they want to squeeze out every bit of performance possible at the high end the Mac Pro / iMac Pro would get their own design separate from the lower end Macs. If they can add a few hundred MHz extra maybe they'll see grabbing an extra 10% of performance as worth it. It would also let them do stuff like giving it wider SVE2 units than the lower end Macs get so they really kick ass on specialized loads and Intel wouldn't be able to match them even with AVX-512 code. It really depends on Apple's goals, and if they've been tasked with the goal of simply and efficiently replacing x86 with ARM, or have been let loose with the additional goal of making Intel look bad while doing so.
