Outsourced to who? The only companies with the engineers you’d need are the other CPU makers like Intel, AMD, Qualcomm, and Nvidia. And none of them make a CPU as efficient as Apple does.
CPU, GPU, neural processor, image signal processor, U1 chip for device tracking, Secure Enclave for biometrics, a 5G modem (only used in the 16e so far)…
They don’t manufacture the chips in house of course. They contract that out to TSMC and other companies.
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.
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.
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.
More likely it was derived from PWRficient, or a clean sheet design that took lessons from it.