It actually states that you may transfer your rights to the game to another person, which is, like... wow.
I'm not sure if I've ever seen this in another steam-connected game.
I still dislike the wording around the fact that the TOS can be changed at any time, and refusing revokes your right to playing it (without any compensation), but that's pretty much industry standard (unfortunately). This however, stood out to me.
P.S: If any of y'all have some extraordinary TOS's for other games that stand out in good (or bad) way feel free to share, it'd be interesting to know if there are others!
Steam does support it. A long time back, I was still new to Steam, and activated a key on a second account I'd created. I opened a support case, told them I'd activated it on the wrong account, and asked them to transfer it. They did.
That's a transfer within the platform, very different from the scenarios I described. There is no method supported by GOG or Steam to transfer a game to a competing platform.
You can't open a support case and tell them "sorry I actually wanted this game on GOG, can you transfer it to my account there?". At best you could ask for a refund, obviously if you've played the game enough you wouldn't even be able to ask for that.