Styles Panel vs Styles Menu operation - why different?

V3.1.5.1 Windows 1- 64-bit.

Can someone shed light on the difference in the way these two operate?

I applied a (character) style using the Styles Panel and later (so Ctrl-Z wasn’t available) decided to remove it by selecting the same text and clicking the same style in the Styles Panel. There was no effect.

However, when (for test purposes) I clicked the same style from the Styles Menu (applying to an already styled selection), the style was removed. (Keyboard shortcuts also toggle style.)

What the reason for the different ways of working? What cool things can I do with them that I couldn’t (easily) do otherwise?

[Plus: would it be possible to show the keyboard shortcuts in the Styles Panel as well as on the menu? The panel can be left open, allowing quick visual access to the list of available keyboard shortcuts for styles]