This is not True FreeCAD is capable of doing such things, and much more:
An example of creating surfaces:
viewtopic.php?t=71181
But joining them is another task, as some things could only be approximated, so the surface is not everytime following the "generating curves", so you have to accept an approxximation and extract new boudaries curves to create the other mating surfaces, but also these could lead to approximated edges, that will not match among them, how to solve these mathematical problems?
But many things could be done in actual FreeCAD as example for every solid object you have access to each one of his surface and place things on his UV space.
viewtopic.php?t=72913
Or more general:
https://dev.opencascade.org/doc/occt-7. ... ct_modat_5
But also.
viewtopic.php?t=65722
It is a matter of knowing how it works, sadly most of these things are not easily achievable with the GUI as you have to manipulate "raw data" of surfaces and use some rules to position things.
Some things are doable with "Curves WB", some other with "Reverse Engineering WB", some by hand, using Python Scripts.
How to translate them to some GUI tools, is another thing, and not easily doable without making some assumptions, that could or "could not" work for everyone needs.
So there are some needs of "thinkers" that can make some abstractions and think of some interface to these complex things, but sadly most of them could not be simply copied by "other software" workflows, as they are tightly related to the "modelling engine" that is OCCT.
I have put together a bunch of python code to make things, and I could do many things at this level, as example curve things to adapt to a cylindrical surface as in some of these examples:
But as said finding a reasonable GUI to make this sort of things it is not easy to do.
It is not very visible, but you can even put holes that will follow the "normal" of the surface, but some things could be achieved only by "trial and errors" and could not be generalized at lest for me for "generic surfaces" as you have to cope with parametric surfaces that are not the same, as example, working with a sphere is not the same as working with a cylinder.
See as example problems relative to mapping in sense of representing the earth on a paper map, this need a projection and there are many ways to do this type of projection, an example:
https://en.wikipedia.org/wiki/Mercator_projection
Hope I have expressed my though in a clear way. (I have many doubts about )
Regards
Carlo D.