I think the " scant 1/4 inch seam allowance" is just another way to say " make sure your seam allowance is no more than 1/4 inch wide."
There are some that think that if "some" - of whatever - is good, "more" will be better.
I also think that many garment sewers have been accustomed to using 5/8. Inch seam allowances. So that may also be part of the emphasis on the narrower seams. After using wide seams, that 1/4 inch does seem very skimpy.
Examples - not exactly quilt related - maybe will help convey the idea.
My FIL would use a heavy-weight four inch nail when a medium weight three inch nail would have been more than adequate.
"Some" salt added to food enhances the flavor. Too much ruins it.
If a size 12 looks good, a size 16 will look dumpy.
If one aspirin will relieve the pain, three should mske it go away faster and the relief last longer. (Not really - but I do know that is how some people think.)
As has been written many times, the seam allwance width is only part of the process of getting something the expected/wanted size.