default or selected kernelversion does not have config value CONFIG_FUNCTION_ALIGNMENT_64B.
Result is shown for kernelversion 6.9.9

CONFIG_FUNCTION_ALIGNMENT_64B (not configurable)

configname: CONFIG_FUNCTION_ALIGNMENT_64B

Linux Kernel Configuration
└─>General architecture-dependent options
└─>FUNCTION_ALIGNMENT_64B
In linux kernel since version 6.2 (release Date: 2023-02-19)