This is one of the problems of Android's model. By being so open to customization, any branch's weirdness gets mixed in with "Android", because there are too many variations and not enough linguistic ability to name them all clearly and consistently in conversation.
Comments
Huh. What manufacturer? When unlocked, stock Android has had incoming calls as a notification rather than whole screen for years.
When screen is locked it is probably still full screen.
Many crap reskins (Samsung, Xiaomi, Huawei) break the ability to hide call notifications. It's absolutely awful.
This is one of the problems of Android's model. By being so open to customization, any branch's weirdness gets mixed in with "Android", because there are too many variations and not enough linguistic ability to name them all clearly and consistently in conversation.