You get the ARM ISA, and compilers that work for ARM will compile to Apple Silicon. It's just that the actual hardware you get, is better than the base design, and therefore beats other ARM processors in benchmarks.
More likely it was derived from PWRficient, or a clean sheet design that took lessons from it.
All they care about is that companies buy an ARM license, not that they use the boilerplate ARM CPU design.
Those designs are there to make it easier for companies to make ARM-based chips who would otherwise never be able to design their own.
https://www.electronicsweekly.com/news/business/finance/arm-...
It is very unlikely Apple uses anything from ARM’s core designs, since that would require paying an additional license fee and Apple was able to design superior cores using its architectural license.