The diagram is not a true representation of reality.
When viewed from the surface on which the shadow is projected.. the light source and the object creating the shadow... are the same size.
This means that the diagram is not too scale.
If what we witness on the earth.. was, in reality, as the diagram describes... then the sun would engulf the moon. The moon would only be a small obstruction within the immense disk of the brightness of the sun...
And... if that was the case.. we would never see the "halo" effect, Baileys beads or the diamond ring, around the sun.
Totality and maximum eclipse: The Moon completely covers the disk of the Sun. Only the Sun's corona is visible. This is the most dramatic stage of a total solar eclipse. At this time, the sky goes dark, temperatures can fall, and birds and animals often go quiet. The midpoint of time of totality is known as the maximum point of the eclipse. Observers in the path of the Moon's umbra may be able to see Baily's beads and the diamond ring effect, just after totality ends. From: A Total Solar Eclipse Isn't Total Everywhere
Don't worry. Even the website that I got the above quote from.. has the same erroneous diagram.
I am not even sure if the people that produce these diagrams are aware of how incorrect they are.. or.. if they cognitively do it intentionally to cover the fact that the shadow of the moon is too small..
Also, there was all this hype at the last solar eclipse where NASA was trying to describe why the moon shadow moves the wrong way across the earths surface...
Just another comedic event in the presentation of the universe around us...
If you just watch and don't ask.. you will never know.