It's not a valid one, because it does not indicate any padding, it merely indicates that either (1) the suit is thin enough to show veins or (2) there is a fake vein. It provides no evidence whatsoever that there is also padding.
There isn't all that much definition really in the muscles except in the abs. Depending on the thickness of the suit itself, definition could certainly show through.
Again, though, it's odd that everywhere on the suit looks natural except for the abs. Why did they screw up the abs so much but get everything else to look so flawless?
You don't think his biceps, triceps and chest are very defined? Gonna have to disagree there. Read my previous post for my thoughts on the abs.