Nope, if you lie them down on the ground horizontally (flat), and star-earth them together that way, then cover the whole area with conductive concrete, you get a more effective earth than simply ramming rods down lengthwise into the ground. Trust me, I've tested (and even measured) it both ways! Well, the electrician did...
That's why in professional installations, they use what's called an earth lattice mat: https://churchillsc.co.uk/earth-mat-lattice-copper
From link above: "Lattice copper earth plates are usually used in situations where its very difficult to knock earth rods into the ground. The plates are usually placed a meter in the ground and because of the surface area will usually generate good readings".
I've done a similar thing with rods, creating a square, and with the final rod running diagonally from corner to corner
I should've really used another one and created a cross in the middle, but at the time didn't think of that until it was too late!
Marco.