Yes, it makes a huge difference...scant vs. regular 1/4" seam. If your machine has a needle adjustment, just move it 1 click over and you will be fine. But believe me...it does make a differnce..ask me how I know :shock:

one click to the right or left? theny need to make a settin: scant 1/4" lol all these new patterns and instructions say it now

I think that the "scant" is to account for the bulk that is made when the seams are pressed to the side.

on some patterns, it would not matter, as long as you had the same consistent seam. but some need that "scant" for the "turn of the cloth" that a seam takes up as it is turned.
sew a sample block, or piece of a block that has lots of seams. see if it is the size it should be. then make your seam smaller or larger as needed.
I think the easiest way to test your seam allowance is to cut 3 of 1 1/2" strips of the fabric you will be using.(about 4" long) sew these together lengthwise, carefully PRESS. measure--the whole piece should be 3 1/2" wide. if larger,you need to take a bigger seam. if smaller, you ned to take a smaller seam. I keep pieces to sew before a major project, but to keep me honest.

Many of us here have found it does make a difference :D
Many of us have found that when we all made the same block from quilterscache, they were too small unless we used a scant 1/4" :D:D:D

The instruction could also be to make us aware that an overly wide seam would cause the block to end up being too small.

I totally understand the confusion of the scant 1/4 inch. I just bought a new Bernina and the lady told me to leave the needle in place as is and not to move it over but its not my "old" 1/4" as in my old machine so I'm moving the needle over anyway. I did the test and it came out right with it moved over....however its aggravating to have to do that since the machine came with the 1/4" foot that isn't really....ugh!!!!

The required scantiness will vary depending on the thinckness of the fabric and thread used, and also how you press, open or to one side. I use a 60 weight cotton thread to piece (YLI) which takes up little room and I ALWAYS do a test block and measure, check points etc before proceeding. My needle position can vary a click either way depending on the fabric, etc, etc. Depends how pernickety you are I guess - I'm VERY pernickety! LOL