As bourbon is matured on new wood, the individual barrel is more or less affecting the bourbon the same way. Things like age, mashbill and warehouse location matters a whole lot more than the barrels, as the barrels are similar. Not so in Scotland where all types of casks are used and they are used many times. So in Scotland you do sometimes see tired casks that doesn't really influence and mature the whisky. One way to repair a whisky from a tired cask is to empty the cask and fill the spirit into another casks. Giving a whisky a huge shot of flavour from an active wine casks is very popular and just months in such a cask can have a huge influence. It's called "finishing", and it's done both to repair tired whisky casks, but also as a flavour design.
But for bourbon, finishing is not very common. The lack of tired casks, and the fact that bourbon itself is fast maturing and very intense is the explanation of this. But finished bourbon do exist and I just happened to have a couple of them in my possesion
Malts of Scotland Bourbon
Heaven Hill, Malts of Scotland, Port Cask finish. 52.8%
distilled 2001, bottled 2015
This is a little bit weird as it tastes more like a cocktail than a bourbon. It is fruity, a bit like bourbon with a dash of blackcurrant. It's very easy drinking, the alcohol is very well integrated. It's a bit more watery than my average bourbon, but also quite woody, which is a bit of a contradiction tastewise. The tasting experience is very unusual for me as I get woody flavours above my tongue and fruity flavours below. I all ends with a sweet finish.
Finishing a bourbon, the effect is much less than when finishing a single malt. This is a bourbon most of all with a little fruity twist. The whisky hasn't lost its soul