I think this is more of a "different people's minds work differently" thing than an age thing. Some people who grew up in the digital age still find analog clock faces more useful. Here's a short youtube video exploring that https://www.youtube.com/watch?v=ZArBfxaPzD8 . I think Adam's mistake was assuming the preference for analog was universal which was probably wrong even when he first wrote the joke.

I think the argument could be made for a clock face being a pie chart if you think of it the way the host of that video does. The categories are "time left in the hour/day" and "time passed in the hour/day".

All that said I was really happy to finally understand what Adams was trying to say with that joke witch, as a person who finds digital readouts more useful, never landed for me before.