Thanks for contacting us. To fix that style you will need to change the deformation mode of the panels from Vertical to Stepped
This will remove the deformation and the panel will be positioned at the height of the spline at the start of the path section. Optionally you could enter a small value for Vertical Bottom so that the gravel board continues to follow the spline while the top remains stepped.
In the existing style the top of the boards continues over the posts so you will need to prevent that by adding and empty segment to the Start,End, Corner, and Evenly inputs of the second generator and enter a Fixed X-Size value of 100 mm to match the size of the posts. You should also set this segment to stepped.
Please find an amended version of the fence style attached with these changes.
I hope that helps, please let me know if you have further questions.