A bit of a tangent but the same byproduct effect is seen in the production of sherry casks for finishing Scotch.

A lot of sherry bodegas only really exist to churn out barrels for whisky distillers.

I love port and sherry finished scotch but I do feel like it’s cheating the idea of single malt.

Glad they do, those who ignore sherry and their brandies are missing out.