Look above the painted arc
IFAB’s Law 17 clarification permits a corner when part of the ball overhangs the corner arc. The whole ball need not sit on the grass inside it. A close-up focused on the bottom of the ball can therefore make a permitted position look incorrect.
Picture a circle viewed from overhead and a ball placed just beyond it. If the ball’s curved side still projects above the painted arc, the lowest point may be outside while part of the ball remains over the relevant area. That is a geometry issue, rather than a special favour to the taker.
Do not confuse setup with activation
The position before the kick is one question; whether the ball has subsequently been kicked and clearly moved is another. A player adjusting the ball with their hands is still setting up. A short kick need not travel out of the corner area to start play.
A useful replay follows the setup and first foot contact continuously. An isolated still can show placement, but it cannot establish whether a short routine had begun. Conversely, an angle showing movement may hide the overhang above the line. Choose the view that answers the actual dispute, and avoid using one cropped picture as proof of both correct placement and a valid start to the routine.
Questions answered
Must every part of the ball be inside the arc?
No; partial overhang above the arc can be sufficient.
Must a short corner leave the corner area to be in play?
No. Kicking it so it clearly moves is the relevant activation.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.