This is pretty far off topic for this discussion - old technology, rather than new. But since I remember trying to explain this to someone, but have no idea who it was, and this seems like such an excellent exposition, here’s the link to
Pivot Tables, Pivot Charts, and Real Charts
by Jon Peltier, MVP
[While you’re there, check out the rest of the TechTrax newsletter. I also watch the LogicalTips newsletter, a related publication,