CONFIG_RISCV_EFFICIENT_UNALIGNED_ACCESS is not available for thedefaultarchitecture x86.
Result is shown for architecture riscv

Assume the system supports fast unaligned memory accesses

configname: CONFIG_RISCV_EFFICIENT_UNALIGNED_ACCESS

Unaligned Accesses Support
└─>Assume the system supports fast unaligned memory accesses
In linux kernel since version 4.19.310 (release Date: 2024-03-15)  
Assume that the system supports fast unaligned memory accesses. When
enabled, this option improves the performance of the kernel on such
systems. However, the kernel and userspace programs will run much more
slowly, or will not be able to run at all, on systems that do not
support efficient unaligned memory accesses.