Whoever conveyed the information is speaking utter nonsense. When oil is heated and comes into touch with the seals, the seals expand due to the heat. If the seal is deteriorating but not completely failed, increased temperature (due to prolonged operation) will cause the seal to expand, hence enhancing its sealing capability.
A little quantity of oil might need a significant duration to combust in an exhaust, since it does not evaporate like water.
If your seals are deteriorating but not completely failed, you may have seepage into the exhaust and potential pressure in the oil drain line, which might force oil back into the crankcase. Once the vehicle reaches operating temperature, the seals may improve somewhat in effectiveness.
Additionally, regarding the PCV system, idling may produce increased smoke in some vehicles if the crankcase pressure exceeds acceptable levels.
When idling, the PCV valve is actuated open by the vacuum generated by the manifold. This compels all gases from the crankcase breather tubes to be sent into the manifold for combustion (emission waste). While driving under boost, the boost pressure within the system forces the valve to close, directing the gases into the intake (post-MAF) and traversing the entire system. This process facilitates the combustion of a greater volume of blow-by as it passes through the turbo, down the pipes, through the intercooler, and subsequently past the throttle body into the manifold, resulting in a more complete combustion.