the quilting recommendations are quite important- and should always be checked- purchase a batt that meets the requirements for the quilting you plan to do- 2"-4" is fairly dense quilting--if it is not done within the (guidelines) the batting will pull apart-ball up and create a lumpy quilt with areas of no batting (because it is all balled up) over time with washings....warm & natural and other batts with scrim allow larger areas to go unquilted but you still need to quilt them to the recommendations. more is ok- less will cause (heart ache) somewhere down the road if the quilt is used and laundered.
every 2"-4" means there should be a line of quilting every 2" to 4" everywhere on the quilt- not just in furrows= they need to be crossed too- it's all over the quilt
you can use batting that needs 10" quilting then just go around blocks but the quilting needs to go in both directions- vertical and horizontal- not just in one direction.

Depends on which batting was used. Warm and natural is every 10 inches, so a 10 inch square would be sufficient. If you took it to an experienced long arm quilter, they should have said something if they thought that the quilting you requested was too light for that batt. You could call them and ask exactly what was used and look up the requirements online to double check.

I agree with all you have said, but I would like to add one thing, the reason it says to quilt every 2-4" is that the quilting will be evenly distributed and this makes the quilt lay better. If you quilt more one way than the other, sometimes your quilt will have pooches and humps that do not "become" the quilt. It will draw your eye to the unquilted area and not to the overall look of the quilt. (Yes, I do professional long arm quilting)
OzarksGma

Thanks for all the replies. I will make sure my quilting is no more than 4 inches in any direction!