RUT955: sim_sel does not work?

According to RUT955 SIM selection?
I finally began to try/test usage of 2 SIMs installed in the RUT955. Unfortunately, I discovered, that "option sim_sel '0/1/2'" in /etc/config/system is simply ignored. Always SIM1 is used, only, even after reboot.

However, I can select SIM2 when modifying

config gpio_switch 'sim_sel'
        option name 'SIM select'
        option gpio_pin '503'
        option value '1' #option value '0' for SIM2

and reboot.

So, it looks like a bug processing "option sim_sel" .
OR, can somebody confirm, that it works on his device ?

After you modify gpio_switch configs in /etc/config/system: You need to reload or restart gpio_switch, the program which sets the gpio values from the gpio_switch configs.
/etc/init.d/gpio_switch reload