Lots of variables, mainly the barrels. If they are using one use bourbon barrels, they still have leftover bourbon in the wood and it raises the ABV. The ABV is likely different every year, they just don’t update since they wouldn’t know the ABV until it comes out of the barrel (at which point the labels were already approved).
I often wonder about the accuracy of listed ABVs. What repercussions (if any) are there for breweries that sell beer that doesn't match up with the listed ABV? What is to stop a brewery from overstating/understating a beer's ABV to boost sales? Is it all just the honor code? There are a couple of beers that come to mind with high listed ABVs that seem a little too "well hidden" and lacking punch to be actually as strong as the label indicates. There was one particular local stout listed at 14% when it came out that I had a really hard time believing. The opposite could be dangerous, too. There's a big difference between 8.5% and 11.75% when spread over a couple of beers. Yes, it is everyone's own responsibility to monitor their consumption, but that it easier to do when working with accurate ABV metrics.
Yeah no kidding. Base beer might have gone in at that, and came out 11.5. Blog from Stone said spirit barrels can add 3%...which would be exactly on mark.