Anyone else's baby not cry if they're poopy?

My Son (5 months old) doesn't make a peep when he's got a poopy nappy/diaper/whatever you want to call it. I regularly change his nappy, usually just before a bottle and about half way between (he gets sore if I leave it any longer). But there have been times (usually just before he's due another bottle) where he's ended sitting in poo for long enough for it to either start drying to his bottom, or leaking out the side, because he hasn't made a single fuss about being poopy. He doesn't cry about it AT ALL. I love that he's a calm baby, but sometimes it doesn't help!