I wouldn’t say this behavior is “normal” – Dogs typically have a strong aversion to laying in their own mess and will not usually use the bathroom in their crates. HOWEVER – its not necessarily abnormal. Has he been examined for urinary tract/bladder infection? Is the crate too large for him – leaving alot of extra space? Do you leave water in his crate while you are away? You could try putting treats in his crate or food – if he associates his crate as more of his own personal space, he may develop the aversion to pottying in it. Placing a blanket or sweatshirt with your scent on it in his crate may help him with separation anxiety – also covering his crate with a light blanket or sheet (creating a “den” like environment) – leaving about 1/4 of the front of the crate uncovered to ensure he’s getting enough oxygen & doesn’t get overheated. Never use the crate as a form of punishment (they need to feel as though the crate is their “safe” place) and never scold or discipline him while he’s in there. Pit’s are slightly “hard-headed”, but they are very intelligent and also have a higher desire to please than many breeds – this is why with appropriate POSITIVE enforcement and consistency – they are very easy to train. 🙂
If the reason he is using the bathroom in his cage is separation anxiety – I think you are going to need to tackle that first before you will see results with the crate. Good Luck!