As you can see, this isn't remotely true.
Election day 2012 was Tuesday November 6th. I've taken polls from PollTracker which were taken entirely in the five pre-election days of November. I've listed them by their last polling date in the field and then ordered them by how close they got to Obama's final margin of 3.9 percentage points.
As you can see, IBD/TIPP was about the middle of the pack when judged against the actual final result. GQR, Rand, ABC/WaPo, Reuters/Ipsos and PPP were all closer than IBD/TIPP. And they were only slightly more accurate than the remaining pollsters on the list.
What IBD may be claiming is that they were closest since they got closest to Obama's absolute number: 50.3 compared to 51.1. But that's not really a measure of anything since they got that be squeezing the undecided number down to close to zero.
The upshot is that this IBD/TIPP as most accurate pollster is demonstrably false, no matter how you want to slice it. That's not to say they are a bad pollster. They were basically in the pack with everyone else in 2012. But what Trumpers are saying is demonstrably false.