It's absolutely true that fat wires will behave at least a little differently from the point-like wires.
But if you are looking for a physical intuition behind the general mathematical form, then the thin-wire limit where you start. Big-wire deviations are an advanced topic, fit for engineers.
N.B. there's a difference between "thin wire" and "point like". I am saying that real wires, with constant-voltage surfaces will _behave_ like point-like charges as they get smaller.
Perhaps I read this wrong, but isn't the opposite story the case? As wires become more point-like, the effective shielding drops to zero. However, when wires become precisely points, shielding becomes perfect?
It dosen't drop to zero. It is worse than for fat wires -- but the maths is easier.
It's intutively obvious that fat wires should shield better (there's just more shielding). But the original author is right that it the explanation of why this works is lacking from the Feynman point-like appraoch.
But if you are looking for a physical intuition behind the general mathematical form, then the thin-wire limit where you start. Big-wire deviations are an advanced topic, fit for engineers.
N.B. there's a difference between "thin wire" and "point like". I am saying that real wires, with constant-voltage surfaces will _behave_ like point-like charges as they get smaller.