i see a diagram there now, might've taken a while to load https://gitdiagram.com/lorlouis/cedit
And yeah it seems to be missing a few connections but the ones that are there are correct line.h depends on str.h which links str.c which depends on xmalloc.c/h.
But had I been a new contributor to the project I would have found the missing links between modules pretty frustrating.
My guess is that the graph is only good enough to give and overview of what things are dependent on what if I were working on a monorepo and I had to justify to my manager that team B needs to do something for us.
I like the idea though, a lot of direct code to graph tools are too noisy and that tends scares non technical people away.