Neuro-visual I think. Hard to see 100s of dots in a circle as not a circle.
The same principle is why this looks like a circle/ellipse but it isn't:
O
The same principle is why this looks like a circle/ellipse but it isn't:
O
https://quickchart.io/sandbox/#%7B%22chart%22%3A%22%7B%5Cn%2...