That would presumably be part of the defense's argument. That even though the game looks similar to IKEA, no one actually thinks it _is_ IKEA.
I'm not saying IKEA has a fool-proof case, or even is really worth the effort, but if people are looking at a thing that looks like IKEA and saying, hey, that's an IKEA, then that's probably enough to get it heard in court.
It's pretty obviously not an IKEA, because you can buy IKEA's products in an IKEA but you can't here. But maybe it's not obvious enough whether or not it's an IKEA ad (think product placement) so if the game incorporates something distasteful then it could get consumers thinking that the real IKEA is running a distasteful ad? If someone tried to run an ad on TV for a company without their permission, I think it would generate similar concern.
Consumers of Weird Al and SNL know that the original artist isn't advertising. Consumers of games might not know that the original company isn't advertising?
I'm not saying IKEA has a fool-proof case, or even is really worth the effort, but if people are looking at a thing that looks like IKEA and saying, hey, that's an IKEA, then that's probably enough to get it heard in court.