If the letters were indeed arranged in service of the alphabet song, they did a terrible job. "G" and "P" are too far apart, so the letters L–P have to be sung really fast for the rhyme to work.

As a very young child, I remember thinking that "LMNO" was one letter, until I watched a Sesame Street segment which explicitly addressed this misconception. Since this segment exists, I clearly wasn't the only child who got confused.