Yeah - I also think this would def work better with one-off projects (like wordpress set up) rather than for projects they have to plan for or need long term
I think one of the hardest things to do, for both non-profits and volunteers, is to identify an appropriate project. One thats sufficiently interesting for volunteers to work on, but manageable within a limited time frame and requiring limited resources, and still useful to a non-profit.
I also think you may be underestimating the effort on the part of the non-profit to get a volunteer up-to-speed with necessary information and to be available to answer volunteers' questions.
An important consideration, for me, is having an easily searchable record of conversations. Because of this, for work-related issues, I definitely prefer email or gchat, which affords almost the same search-ability. What I hate most are medium-switches when conversation threads are spread across emails, gchats, and texts.
I think the term "CS illiterate" is not offensive in-and-of itself, especially since it was clearly meant facetiously. However, I think you conflate being cs illiterate (not knowing how to code) with not knowing how to use technology intelligently and being vaguely technophobic (e.g., saving all your files on the desktop). I don't think knowing how to upload data to github leads to cs literacy, but it does seem to be a marker of participation in the cs community and in this case, at least, allows access to others with more cs expertise.