That would sufficient to carbonate an English ale without priming sugar.
AKA measurement error.
It amazes me that people believe their measurements are that precise, especially as many hydrometers only have a resolution of 0.002.
IIRC from the days when I studied science, measure AT LEAST 3 times and average the results. Or maybe if 2 of them are the same, assume they're right and the other one is an error. However, far from guaranteed!
It's a bit like when working with materials to be cut: Measure twice, cut once!
I have 2 hydrometers and a refractometer (and the dreaded Tilt hydrometer, but let's not start that over again...). Not sure I've ever known them all to agree on a gravity reading!