I moisten the board faces, along the edges, not the glue joint faces.
My idea of moistening the board's faces is to prevent the squeeze-out
from adhering to or penetrating into the faces, causing a "show-line",
after the glue has dried. I do wet-wipe the squeeze-out, also, once
clamped. Pre-wetting seems to allow for easier clean-up, also. I've
always reasoned this initial wetting helps prevent any glue
penetration into the faces, not assist with penetration. Seems to
work for me.
I would think, if a glue needs penetration assistance, then it should/
would be written on the bottle/container as so.