MiKTeX packaging mechanism: Does it exclude runtime relevant .tex files?

[LLdaniel]

Hi there,
I try to get a better understanding for how CTAN sources are organized in MiKTeX, especially when a package contains a runtime relevant .tex file. Is there any way to flag a file to be runtime relevant? Or is it recommended to simply name relevant files as .sty?

I would be glad if someone can point me to the documentation/code where .tex files are filtered.
That this happens seems to be a likely assumption as of moderncv/moderncv#199, where a runtime relevant .tex file cannot be found:

! LaTeX Error: File `moderncvcolors.tex' not found.

Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: tex)

Thank you in advance!