I don't trim off my batting until after I've put on the first machine stitching of the binding, and I use that seam for my measurement.
I cut my bindings a bit fuller than most, at 3" and so I trim .5" from that seam line for a nice full binding. When we say "full" that doesn't mean round, just the same as the body of the quilt.
If you have a half inch finished binding and you trimmed everything at 1/4" that means half your binding is empty.
You can add in little wisps of left over batting if you need to.
Edit: It's not that big a deal really, but if you want to show your quilts it is expected (along with mitered corners). Doesn't impact the kindness of a gift or the durability of the quilt. For the first couple of decades of my quilting I used straight bindings with butt joints. Decided to switch to bias French double fold binding and miter corners because that was the expectation/standard but mostly I just say Boo to the quilt police
