Far as similes go, I’d say that’s closer to arguing that, when taking a pie from an open windowsill while the owner isn’t watching, it is acceptable to also take the neighbour’s cutlery and a plate (which were coincidentally currently in the pie-owner’s house, probably because they’re on good terms with one another and maybe having a party or something) along with it, because those were made to be used with edible things. … although, naturally, the “The original is not gone if I take it”-nature of digital content changes the situation a little.
It’s overall pretty easy to piss people off, even the most easygoing ones. I wouldn’t bet a Steam account that has money in it on that potential pissed-off authors will accept “Your work was made to be used” as a valid argument and refrain from causing trouble for the migrator. Honestly, I think that’s likely to make things worse; if someone feels that you’ve done them wrong and disrespected them, and you field that one, they’ll probably hear “I was fully within my rights to do what I did, and I am wholly unapologetic, and you are in the wrong for complaining!”. Something like “(Author Name), I love your work, I tried to contact you but I couldn’t figure out how to reach you. Here, can I pass this thing back to you? It’s so great that you’re back!” would probably work better.
But that’s neither here nor there far as the way the hosting platforms need to react to protect themselves in accordance with real-world laws goes. :-/ If the legal owner complains, the migrator is considered at fault. What anybody else here thinks about content being migrated doesn’t really matter far as that goes; we are not legally authorized to speak on behalf of anyone’s work other than our own. Point being, if somebody gets pissed, we can’t protect the migrator. :-/
And some of us have made pretty bad prior experiences with people just taking their stuff, too. It’s not super unlikely that at least some folks hereabouts would take unauthorized migrations of their (or somebody else’s) work poorly, and want to smack migrators down on principle. :x And yet some others are financially invested in their intellectual property, and thus take infringement on it very seriously.
It’s pretty annoying when you just want to play games and promote stuff you love, I know. :-/ Imagine what the legal situation would be like for persecuting intentional, not-at-all-well-intentioned IP theft that actually hurts people financially if it was otherwise, though. Situation overall kinda sucks. Personally, I blame evolution. ^^