Barrel aging increases abv of spirits ? Beer ?

[Jokester]

When spirits are put in new barrels, I thought more alcohol evaporates, and more alcohol enters the wood compared to water and hence its quantity and proof gets lower. Angels share or something like that.
If they're put in used barrels like scotch - I thought the same thing happens but to a lesser extent.
Beer is put in used bourbon barrels for a lot shorter time usually, and again does the same thing happen ? Also does beer ferment in the barrel also - or is it pasterized before being put in the barrel ? Someone who works at total wine seemed to claim 5-6% abv increases from the barrel aging alone for the dragon milk stout.

 

[lumpher]

Somebody is on crack. If beer ferments in barrels, it was put in with residual sugar. If it increased 5-6%, they put it in barrels when it was still sugar water, and i hope they didn't seal the barrels...

 

[Jokester]

It is 12% abv as bottled. Barrels have a little leakage and loss of liquid, so they sort of breathe. With Co2 it may lose more, well enough to be a "vent" of course contamination is a huge risk. Anyway I am trying to find out what exactly happens in the barrels in these cases listed above.