Red/Green Accept/Decline Buttons vs Slider on incoming calls

New iPhone XMax. On some incoming calls, I get the green/ red "Accept" or "Decline" buttons, which I prefer because all I have to do is hit Decline if I don't want to answer.

On about 1/2 my incoming calls, those two colored buttons do not show up; instead I get the slider that says "Slide to Answer." I'm aware I can stop the ringing by hitting the upper side button, but that doesn't send it to VM as quickly.

What determines which incoming calls bring up the 2 colored buttons and which bring up the slider? And is there a setting to make all calls bring up the colored buttons?