I think your question is -
as a shop-owner or manager -
If a customer asks for a quarter of a yard - can you sell exactly 9 inches of fabric or an exact 18" long FQ - and have the customer leaving the store a happy camper?
I am always happy to get more/extra - but I won't "fuss" if I get AT LEAST what I ask for. I may not go back, but I won't go out of my way to bad-mouth the store.
I always re-measure my fabrics when I get home. I get ****** if I'm even shorted an 1/8 of an inch. I will at least call and let the store know I was not happy. And then I do my "negative advertising"
I usually buy "extra" to allow for all those annoying things, but I don't feel the shop owner/manager is responsible to "compensate" for them by cutting more than asked for. UNLESS the fabric is flawed.