Steps to reproduce:
# Draw a spline GameObject>Spline>Draw Splines Tool...
# Add a Spline Extrude component to the same spline object
# Duplicate the spline game object from step 1
# Change its shape so that it would be clearly different than spline 1
# Observe the inspector/scene view - the Mesh Renderer for the duplicated spline references the same mesh

Expected result: a new mesh is created and assigned

Actual result: the same mesh remains attached to the duplicated Mesh Renderer with Spline Extrude

Note: this behaviour appears incorrect/unintuitive because re-adding the Spline Extrude component always creates a new mesh. It would seem logical to also do that for duplicated objects.

Reproducible with: 2021.3.31f1, 2022.3.12f1, 2023.2.0b15, 2023.3.0a12