Apple took the ARM base design (they licensed it), and then they modified and tweaked it.
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.
It's more than that. They have an unlimited license to arm designs, and can change them as they see fit, since they were an early investors (or something along those lines). Other manufacturers can't get these terms, or if they can, it will be prohibtly expensive
The thing about Apple having a “special license” due to being a partial founder of Arm is an urban legend. They have an architectural license, just like several other companies making custom Arm CPUs do.
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.
