That is for arm32 userspace binaries being run under an arm64 kernel, and applies only to the handful of instructions which in Armv8 still generate alignment fa

That is for arm32 userspace binaries being run under an arm64 kernel, and applies only to the handful of instructions which in Armv8 still generate alignment faults. With an arm32 kernel you could configure the kernel to fix those up as well; with an arm64 kernel you cannot. This only really matters for broken programs which do unaligned accesses without telling the compiler about it (which can also trip you up, though more rarely, under x86, if the compiler decides to use a simd instruction). As Steve says, it only affects a really tiny set of programs, which can have their bugs fixed.