Extra geometry reported in variable layer thickness slabs

Hi, just noticed that slabs with variable layer thickness edited using the Modify subelements tool are exported in a wrong way: there is a vertical extra surface not present in Revit causing a bigger bounding-box and a wrong value of Width and GrossVolume in BaseQuantites tab.
I checked architectural slab and structural slab, both have the same issue.
Attached is a basic model. I used the last 22.4.1.0 and the previous 22.4.0.0 for Revit 2022

[VariableSlab.zip](https://github.com/Autodesk/revit-ifc/files/8644680/VariableSlab.zip)

Thanks

Start by opening the attached VariableSlab.zip in Revit 2022 and reproducing the export with versions 22.4.1.0 and 22.4.0.0, checking the resulting geometry and BaseQuantities values against Revit. Done means variable-thickness architectural and structural slabs no longer contain the extra vertical surface or report incorrect Width and GrossVolume values.

Written by the indexing model from the issue text.