[Google Pixel Fold] simplepinoi177:
I've been with the Pixel line since the Pixel 2 XL.

From my understanding, I believe the reason Verizon locks it down is because there are bypasses to things they charge (primarily tethering/hotspot, among other services) -- I mean, of course it should be for a greedy reason.

There was a member (like you who was just getting deep into android development) who was really really trying to get into it. They were going about it much of the same you were thinking in terms of somehow bypassing & forcing "OEM unlocking" tick; let me see if I can find the posts.....

Spoiler content hidden.

It looks like he's given up -- but I'll admit he seemingly made some considerable progress.

What I think the thing is that it can't just be about "forcing" or tricking the "OEM unlocking" tick. It seems that Google sets aside a batch of phones that become Verizon variants -- if/when the fresh device coming out of the factory gets activated on Verizon's networks, it probably does something similar to Samsung KNOX tripping (which, if you are unaware, seems/is-supposedly to be a physical trigger on the system board), then the device is reset to be ready for the consumer. I base this conclusion because when I got my Pixel 2 XL Verizon variant, because there was prevalent launch issues (screen, bugs) (to the point they extended manufacturer's warranty by a year more making it have a 2-year manufacturer's warranty), they were inundated with RMA's. I sent mine and my wife's for a replacement and found out that, if I activated the device without inserting the Verizon SIM, I could unlock the bootloader (worked for so many others, but it seemed that those who input their SIM cards it wouldn't work)! It looked like, as Verizon was inundated with RMA's, they just pleaded/arranged to replace the units from Google in whatever they could spare/had-available; including non-variant models. Further issues arose when my phone needed to be replaced once again a year later, and every replacement I got -- because mine was marked as a Verizon variant -- I couldn't unlock the bootloader. I tried to work around this and get it replaced by Google stating/showing my IMEI wasn't a Verizon variant (interestingly enough, when I did the IMEI checkers, it would come back as neither VZW variant or GOOG variant, but "UNKNOWN"; but it seems that in Google's systems, my device & account was linked to a Verizon one, so that's what they would send); but it just confused the rep where they would just send me a non-unlockable bootloader variant (since even if my IMEI showed a non-carrier variant, my account in their system showed otherwise; i.e. my original was a Verizon variant, replaced with a RMA). I was able to successfully get a unit that got me there somewhat -- Any/Every time I factory reset the phone, the "OEM unlocking" tick could be ticked, but once I booted into fastboot and/or after I rebooted more than 3 times, the tick would grey out, as well as the fastboot command to unlock would never work. I brought it to get "repaired" at uBreakiFix, but as they replaced the system board (but probably from Verizon spare parts as that was supposedly where my device is from; not going off of my IMEI but my account with Google it seems), it just came back as a grey "OEM unlocking".

TL;DR I was even able to get "OEM unlocking" ticked on a Verizon variant, and it still wasn't enough.

Hopefully all of this will get you on the right track to eventually figuring this out (but I have to say I wouldn't hold my breath). I would really like to purchase Verizon variants as the incentives are better and being able to finance & pay for it with my regular cell phone bill is most preferable.