[QGIS-Developer] Confused by Point vs. PointZ and LineString v. LineStringZ

[C Hamilton]

I have been writing some code that maintains the Z dimension for vector
layers. When I create a layer from QGIS points whether it is a point or
line layer and I create the points with QgsPoint(x, y, altitude), I can do
this without using PointZ or LineStringZ layers and it maintains the Z axis.

What is the purpose of PointZ, LineStringZ, and PolygonZ? Is there a reason
I should be using them when Point, LineString, and Polygon seem to work the
same? Is there a reason I should not use the Z versions?

Thanks,

Calvin
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