It's not hence why the star k is meikel.
Star K is not meikel - from their website:
Bourbon, Rye, Tennessee and all American Whiskeys- Unflavored
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Certification status: Acceptable WITHOUT Certification
Excluding : SOME varieties that are not recommended due to Chametz She'avar Alav Ha'Pesach issues or aging in Wine Casks, mentioned on label.
Aging in bourbon is nothing compared to scotch and FWIU it gets moved multiple times during the aging process plus they don't age it themselves rather they outsource it
Major distilleries all have their own aging warehouses, in fact in
this article Buffalo Trace is used as an example. Good Bourbon is usually 5 or more years old. Only new upstarts, who don't have their own aged stock will outsource, or store brands and the like.