Okay, it's evident what's happening. Each time VP is installed (no need to re-download), there are subtle feature/operational differences - for marketing A/B testing.
It can take repeated reinstalls to produce the desired result and, in the future, the behavior that most users seem to prefer may become permanent.
After comparing the modes, my preference now jibes with yours: double-clicking the timeline number strip it plays, double-clicking a thumb switches.