Oh yeah, don't ya know, bigger is always better. ;-) lol kidding... You are correct in what you are thinking. It happens all the time, it's always a good catch and a relatively easy one to fix. Another good one is when welding on lets say two pieces of 1/4" thick material in a fillet weld on both sides, they don't need to call out a 1/4" fillet size just because they're welding on 1/4" material.