Very interesting.
I find it difficult to relate to the use of figures in calculating the glide.
In my gliding days when the Swallow or Capstan was the epitome of performance, we used the 45 degree rule - ie if your field was in the arc subtended from immediately below you to halfway to the horizon - you could reach it. Any flatter and you were stuffed.
Use of angles was great in that it was independent of height - very useful for x/c flight and landing 'aux vaches'
Since I started in power and use strips rather than airfields, that skill has served me well.