The most common problem with baby boys “leaking” is based on male anatomy. During a diaper change, you’ll typically have the baby on his back. The baby’s little penis may flop every random direction. If it’s pointing upwards when you put the diaper on, there’s a good chance that you get some spillage at the top and a mostly dry diaper, especially if a little erection causes the diaper to “tent” or pushes the waist band away a bit.
So always make sure it’s pointing down, that should reduce the risk of spilling and get better absorption in the diaper. If that doesn’t help, it may be time for the next diaper size.