If you do a partial section through a mesh, it seems to extend it by default rather than partially, as you would with a surface. Tested on a basic cube (I separated it out here, section curve is top right.
Yeah, I think that is on the pile, I’ll double-check - I know I’ve run into this myself.
Turns out this is not just an oversight as it might seem - the intersection code for meshes did not allow it.
Fixed in V7/WIP.
RH-46543 Section: ExtendSection=No does not work on meshes.
-Pascal
Makes sense that it could be more tricky to intersect I suppose.