The LQS justify the rip because it guarantees the "cut" is on the straight of grain. But in quilting, it does not matter because we all cut and use bias and off grain cuts. Also the fabric is so tightly woven, you can often not pull it into square anyway. Lastly, the manufactures often sloppily print on not straight of grain, and if you straighten it, your print will be off (this should not ever happen in expensive fabric that we are buying, but often does in cheap fabric.
That said, when you make draperies, you MUST always straighten the grain, because what you don't pull to straighten, will slowly "hang out to square" over time on the rod. But grain straightening, in the fabric as well as the lining is always done by "pull a thread crosswise and cutting with scissors along the pull" to avoid the rip distortion and frayed edge. In dressmaking, you should straighten the grain too, to avoid uneven "draping" of skirts and garments.
The only time I straighten the grain in quiltmaking, is on the boarders, if I am going to wall hang it, for the same reason, to protect the drape, although it is highly unlikely it can hang out to square AFTER it is sandwiched to a backing and batting and quilted to turn it into basically one cloth. So I am probably wasting my time.
None of this info helps you in a LQS. You can ask them not to rip, but they probably won't do it, because they want to be "consistent" rather than provided good customer service and do as you ask. But it doesn't hurt to ask them. Poor customer service always results in you having a story to tell many friends, and hurts their business.
Sorry to be so long winded. Hope this helps you