The Dock

I recently activated my new Apple iMac 21.5 (2019/2020). MacOS is Big Sur 11.4.

the dock, like all my past docks holds about 12 Apps I want permanently available on the desktop (eg: Mail). As I open an app from my application folder, its icon appears in the dock before the trash and after the last permanent app. On my past Macs (including my MacBook Pro (2016), when I quit an open app, the icon disappears from the dock automatically. Not now. After quitting I have to right on the icon, choose options, then left click on remove from dock. In some cases clicking on the icon doesn't give me full options, but a quit choice is available which when clicked disappears the icon. It's annoying my past experience.

I probably missed a setup choice, but I've looked high and low and can't find the choice in Settings. What am I missing? Or is this a new feature in 11.4?