Sure, functionally OpenSCAD is just a subset of FreeCAD. The problem is, I can't really trust them if they also push out less robust or outright unreliable features alongside them.
> Even after reverting to old parameters, the sketch will be now be stuck in this new configuration
I have definitely experienced that too. Constraint-based design is very powerful, when it works. But it doesn't always work. A boolean operation always has a result (at least in theory), but a set of constraints doesn't always have exactly one solution, or any solution at all. Which would be okay if the program could reliably tell when something is well-constrained, so that changing a parameter doesn't make it jump to a different solution - one that isn't even on the face I'm trying to make a hole into - which causes the hole and the faces created by the hole to cease existing - along with the sketch I drew on one of those faces that now doesn't exist and so neither does my sketch... It all collapses so easily. How to keep track of faces that jump in and out of existence as the parameters defining them change would probably be a good PhD thesis topic.
> Sure, functionally OpenSCAD is just a subset of FreeCAD. The problem is, I can't really trust them if they also push out less robust or outright unreliable features alongside them.
I feel like I perhaps needed to further emphasize the separation between Workbenches. FreeCAD workbenches can interoperate, to a degree, and the output from one can be used in another. Moving through Workbenches is a part of advanced FreeCAD use. However, they are separate and largely self-contained tools. Different Workbenches operate in different manners not just in regards to the interface but also in regards to their underlying function.
The Sketcher Workbench is where the constraints system is, and mainly exists to support the PartDesign Workbench. The Part Workbench is a decent CSG modeling system that works mostly like OpenSCAD or any other boolean operation based modeling system. It is not reliant on the Sketcher Workbench constraints system. You could use a Sketcher Workbench created Sketch to create a Part solid, but you can also use the output of the Draft Workbench (which could even be based on an imported SVG). It also has primitives, so you can model from primitives.
FreeCAD is intended to be modular. It has a ton of Workbenches and there are more available as addons. How things work in one Workbench is not how things work in other Workbenches, and shortcomings in one should not be projected onto others. If you find OpenSCAD useful, I seriously suggest giving FreeCAD's Part workbench a try. I found that the same sort of modeling I did in OpenSCAD was often easier in FreeCAD and it has fillets to boot. I now use the PartDesign workbench more than I do the Part workbench, but I have a nice cosplay prop I drew in Inkscape and then modeled in the Part Workbench after giving up on doing the same thing in OpenSCAD.
I also feel that it is a bit unfair to say you can't trust them. The PartDesign workbench is the most popular, most complex, and most fragile workbench, but I've never seen it take a step back - every stable update has improved its function and reliability. What's more, unlike many open source projects the 'new shiny' (in this case Part Design) has not been forced on people who are using other parts of the project. It's not intended to replace the rest of FreeCAD, but specifically aimed at people looking to model complex solids in a manner comparable to commercial CAD programs, even if the workflow is very different.
edit: The only universal problem in FreeCAD is the topological naming problem, and it almost never comes up outside of PartDesign because outside of PartDesign features are rarely reliant on referencing individual components of a shape by name. CSG modeling isn't really subject to the topological naming problem.
> Even after reverting to old parameters, the sketch will be now be stuck in this new configuration
I have definitely experienced that too. Constraint-based design is very powerful, when it works. But it doesn't always work. A boolean operation always has a result (at least in theory), but a set of constraints doesn't always have exactly one solution, or any solution at all. Which would be okay if the program could reliably tell when something is well-constrained, so that changing a parameter doesn't make it jump to a different solution - one that isn't even on the face I'm trying to make a hole into - which causes the hole and the faces created by the hole to cease existing - along with the sketch I drew on one of those faces that now doesn't exist and so neither does my sketch... It all collapses so easily. How to keep track of faces that jump in and out of existence as the parameters defining them change would probably be a good PhD thesis topic.