My experience has been the same as zeus; I've been cutting those bigger patches in half for decades.
However, I have had a couple of these peel up on the thick cut edge, long ago. That led me to taking more time with such patches: making sure that the tube is well abraded and partly inflated, that the glue runs right to the edge, that the edges are firmly pressed into the underlying rubber. With these precautions, I never lose air on a cut patch.
However, if I was stuck doing a roadside repair, I would always choose a whole patch.
(As an aside, why do they include those monster size patches in a bicycle tube repair kit anyway? If a hole was big enough to need a patch that big, you'd never be patching it.)