Onshape is just a GUI over the Parasolid geometric modeling kernel, the same kernel used by Solidworks [1]. Whatever their scripting primitives are, they're at best a thin wrapper over Parasolid (which is true for the entire industry - it's all Siemens Parasolid and Dassault ACIS).

[1] https://en.wikipedia.org/wiki/Parasolid#Applications

Yes, this is all true, but the comment I responded to wanted to be able to basically code rather than GUI sometimes , but still have the GUI up to date. Because of how onshape was built it makes this very very easy. Solidworks very much does not. Fusion360 also has good enough python bindings but it's still nowhere near as easy or integrated to do this (or debug it) as onshape.

So I'm kinda not sure what you are going for here. The fact that they are all the same kernels under the cover is sort of irrelevant. It's not that thin a layer and the layer matters a lot since it is what you get to use. It's like saying all of userspace is just syscalls. That's not what users see or interact with, the layer they interact with matters a lot to them.

And both of them were written by Ian Braid, Alan Grayer, and Charles Lang (and others) in Cambridge.

Parasolid was v1 and old school C, then they got the C++ bug like many of us at the time and did ACIS as v2.