Meshlabserver only seems to export triangle based meshes. No polygons are exported.
In the regular Meshlab client you have the "polygonal" option checked by default.
There is no flag to turn this on in meshlabserver.
All meshes that use any sort of triangle to quad filter are useless, since the result is triangulated when meshlabserver exports.
confirming this issue, and looking for a solution, thanks.