Works fine for me. Any reason why you are going for an advanced configuration with all the additional options? My interface section looks a LOT simpler:
config wifi-iface 'wifinet3'
option ssid 'REDACTED'
option device 'radio1'
option isolate '1'
option ieee80211r '1'
option ft_over_ds '1'
option key 'REDACTED'
option network 'untrusted'
option mode 'ap'
option ft_psk_generate_local '1'
option encryption 'psk2+ccmp'
Also, what OpenWRT version are you running?
Edit: That reddit topic is OLD. You no longer need to configure r0kh, r1kh, nasid, mobility domain, r1_key_holder, etc. They are now intelligently automatically generated by hashing the SSID. As long as you are using the same SSID on both APs on which you have that enabled, it should work out of the box with the simple configuration I am using.