Should CTOs Code?
Usually, yes. However, it depends upon the business.
For a tech startup where the CTO is one of a small team of founders building a software product, well then yes it might even be more like 60-80% time in that case. But in a global 2k enterprise with 20,000 employees, I doubt the CTO would have a moment to spare for hands on coding, although I suspect many do maintain some tech skills through classes or hobbies.
That said, I think for many SMB and startups, a CTO that spends 20-50% time coding experimental features in order to plumb the various risks/rewards of new and emerging technologies seems like a proper CTO coding practice.
Coding skills require constant use, and logically the more technical any CxO is the better the understanding behind various technical strategic decision making. Furthermore, “R&D” style with some cross-integration of the code with the main production line is a great use of CTO coding time.
With this approach, new tech strategy and operational methodology can be assessed by the CTO at a high (C) level, and integrated into main line code as test cases and feature “scaffolding” which can then be fleshed out by the production coders.