I take issue with this article because it would come across to me as a red flag about work-life balance. That an employer would expect you to be doing something programming related in your spare time comes across as a bit self-serving.

Instead, I would ask "What would you like to develop in your spare time, if you had any?" That way they can answer the same as his question if they are working on stuff, but can still show interest in programming otherwise.

Frankly, yeah, it can be hard to stay on top of things, and companies that don't foster learning and expect you to do it all on your own time don't help.