In a Planar section it is possible to set a mark in the model tab "Include quilts". So also the welds are removed in the section. First thing that comes in mind is why this option is there, in which situation you DON'T want to include the quilts? But the real problem is, this mark is not available when you create an offset section.
"Include quilts" option available in planar section."Include quilts" option not available in offset section.