I did screw up here. But ask yourself this... If Samsung really wants to have people benefit from the trade in program, could they not maybe email me and ask me for the pin to get in? Charge me $100 for the mistake or something rather than just flat decline? It took me all of 15 seconds to get it back to a point where I could do a FR again with no accounts. The way this program is setup is counting on a good group of people screwing up the return. If that wasn't the case, they'd sort it out or make it way easier.
I traded in 2 phones at T-Mobile in the past. Was the easiest thing in the world. No problems. Similarly at Best Buy. They spent time to make sure everything was done etc. I did not remove my Google account prior to Erase All and Factory Reset in both of those cases. It was never issue. I love Samsung phones and TVs. But not just based on this experience, also some others, I feel they still have a long way to go to become a good customer service company (even if their margins are admittedly way lower than say Apple).