SPG opens with this beautiful statement about the exceptionality of having Strenght superior to 18.
Something which AD&D never stressed enough, maybe- or something that the average player seems not to understand properly.
A characteristic above 18 should require Magic in order to be bestowed upon a human being, otherwise SPG gives the possibility of it being "very rare"- that is, maybe Magic is not necessary to attain it, but in some way or another it can be gained- provided it is a very rare happening.
Remember, a being of Strenght 24 is a monster capable of crushing a man in plate armor with a single blow
Here we enter immediately into the realism that Sword's path glory strives to achieve, from the very first chapter. No excuses. Conbat is a serious thing- we are playing fantasy but if we are to deal with Combat, we cannot but take into account concepts such as this first one, it seems.