Yeah, the exact same thing happened to my partner. Did the same at first to redirect, but ended up deciding against it since it brought more visibility and players to a very niche multiplayer game.
Especially for an online game, it’s probably a win. If you have an ingame store, more people playing = more people buying.
Offline games are more problematic. Piracy is a big deal just because there’s not much incentive to pay for anything. People are lazy and often take the path of least resistance. If your game pops up on piratebay for free, people are less inclined to pay for it.
I keep talking about piracy here because it’s conceptually similar to the iframe hijack thing. They’re “pirating the content” in that sense. But sometimes it’s smart to let piracy happen.