Brandied blueberries must be water-bath canned

This weekend, I mentioned on Twitter that I was canning some brandied blueberries:

Three pints of brandied blueberries processing in the canner now = me looking forward to winter
— Michele Grant (@opadit) July 6, 2014

The comment prompted a pal to ask:

@opadit Do those really need canning, or does the brandy preserve them?
— Brett Heller (@hellerbee) July 7, 2014

I responded:

@hellerbee Need canning because not totally submerged in alcohol; liquid is mostly a very light syrup, only about 15% brandy.
— Michele Grant (@opadit) July 7, 2014

And then I realized that I really, really wanted to go on and give @hellerbee a better, more complete explanation by unpacking the questions he may or may not have known he was actually asking with his tweet. So here goes . . .