default or selected kernelversion does not have config value CONFIG_LEDS_BLINK.
Result is shown for kernelversion 5.13-rc2

LED Blink support

configname: CONFIG_LEDS_BLINK

Linux Kernel Configuration
└─>Device Drivers
└─>LED Support
└─>LED Blink support
In linux kernel since version 5.12 (release Date: 2021-04-25)  
This option enables blink support for the leds class.
If unsure, say Y.