PR: Psets with IFCElement are not exported, exports only as IFCRoot

### Problem Description

I encountered an issue while trying to export classification parameters from a custom user-defined property set in Revit. In my .txt PSet file, I had specified the instance as IFCElement, but the parameters were not being exported to the IFC file—regardless of the Revit version I used (2022, 2023, 2024, or 2025).

After some troubleshooting, I compared it with a different .txt PSet file where the instance was defined as IFCRoot. I updated my original file to use IFCRoot instead of IFCElement, and the export worked as expected.

So if you run into a similar issue with parameters not exporting, make sure to check whether IFCRoot might be the correct instance to use instead of IFCElement.


### Revit Version

2025.4.x

### IFC for Revit Addon Version

25.4.0

### Windows Version

11 24H2

Reproduce the export with the reported Revit 2025.4.x and IFC for Revit 25.4.0 versions, using a custom .txt property set with the instance set to IFCElement. Compare the resulting IFC output with the same property set configured as IFCRoot; no source file or test entry point is identified, so completion would require defining the expected IFCElement behavior and adding a regression check.

Written by the indexing model from the issue text.