I am so tired of hearing this endorsement from diapers and having people say, "well you must be taping the diaper wrong."
The amount of urine different people expel is different. This can range from 150 ml to 750 ml. If you are on the lower end of that scale for your average urination you will not have any problem with any diaper, but if you are on the upper end of that scale then, yes you can and possibly will leak, even on the first time into the diaper.
Picture peeing 3x4 wettings worth into a diaper at once. This is simply too much for even the best diaper to absorb quickly enough to not leak. Let's say you are also sitting down or in the car. Well now you have half the usable space so naturally the urine is going to go up, and leak out the upper sides.
People cannot assume that everyone is the same in their endorsements or criticisms of diapers. When making statements, it should include how MUCH you urinate per wetting, because saying 3-5 wettings really does not tell anyone what your diaper is encountering.