Performance & battery · Performance modes
When does Automatic mode choose Rich?
Short answer: Automatic picks Rich only on a well-equipped, mostly idle Mac that's plugged in with Low Power Mode off. On battery it stops at Good, which still shows full content and charts. You can choose Rich yourself.
Automatic only picks Rich — the level with the most background budget and full effects — when your Mac is plugged in, Low Power Mode is off, the Mac has plenty of processor cores and memory, and it's mostly idle. On battery it caps itself at Good, so it never spends battery on maximum background work.
So it's normal for a laptop on battery, or a smaller Mac, to sit at Auto · Good most of the time. Good still shows full content and charts.
If you want Rich anyway, choose it from the performance menu.