This (hack) is a new one for me. I got the checkin succeeded, but OEM unlock is still grayed out. I will look into it. My 6a was ordered as unlocked not carrier connected.
View attachment 5779023
I've tried the resets with/without sim/internet (at least a dozen) but not until I'd updated to 13.
Getprop gives me
View attachment 5779027. I don't know if that means I don't have it toggled, or that I'm not allowed to have it toggled. I have also checked my IMEI at various phone service sites to see if the device qualifies for another service. It always shows as qualifying. Google knows what I ordered.
I've been ordering unlocked phones (and a few tablets) from Google since the Galaxy nexus (only Samsung phone I've ever had). This is the only one I've ever received with this issue.