It's not a myth --- it's physics, pure and simple.
The potential developed across an inductor is V = -L di/dt.
Accepting the 4.5:1 ratio as a good precaution against strikes to primary
circuit, and striving towards as small a resistance as possible in the
secondary coil.
How does it make sence to use more turns than those that allow the build up
of a voltage higher than that limited by the transfer of energy from the
primary capacitor to the secondary capacitance?