I remember doing a test for it too.
As for this discussion, I'm in the camp that if its shown in any way that he's been traded on the FRONT of the card, the new team should be used. If its only mentioned on the back (and only briefly as depicted on those three cards), they should show the team featured on the FRONT of the card. Part of my reasoning is because when I was growing up and using binders, I put cards on the front and back side of pages (so 18 cards a page) and the backs weren't shown. If I never pulled the card back out, I'd have no way of knowing the player was traded or signed elsewhere unless it was shown on the front.
Having said that, I'm okay with whatever, but I do think a happy medium would be linking the card to both teams. We have that option and while it would add a lot of new cards for team collectors maybe adding a toggle of excluding multi linked cards could be an otion (like the VAR option does now). I have a few Royals in my collection that were traded but still in Royals uniform, and had to seek them out. I would much rather have the option of deciding for myself if I want to include them or not.
Royal Card Review is my blog if you feel like checking it out, thanks if you do!- royalcardreview.blogspot.com/
In the process of updating my collection so don't trust any of my lists right now.