There are already nearly 5 billion ARM devices in daily use globally. An additional 20 million per year isn't significant.
Of these 5 billion ARM devices in daily use, how many are desktop computers running desktop computer software?
What does it matter? Software for majority of these devices is compiled with exactly the same two compilers as on desktop (GCC and Clang+LLVM).
It matters because their uses is different, which forces different design requirements, memory constraints, different multitasking and network environments and assumptions...
Also, for a large number of these devices, they run Java-ish code on a Java-ish VM.
Very few, however native desktop applications are becoming a rarity these days anyway. A small number of professional apps and games, but game engines are already targeting ARM due to phones.
That made me think of an interesting point. I wonder how much of the M1's performance comes from just being able to press the reset button on backwards compatibility? In other words, if I take a latest generation AMD processor and compile every binary for it with all of the processor specific optimisations enabled how much faster would it be.