Manual withdrawal is one thing because it happens and we can talk about that later but network congestion is not that important. When blockchain is clogged and your money is not coming that quickly that doesn't mean it is not coming, if that is the problem 99% of the time you see it not coming but sent, so the money is no longer in mintdice control but it is also not under your control, the money is basically "on the way" so it doesn't mean anything that it takes time, as long as it is coming and on the way, it will eventually reach, at most 48 hours but still it is coming and you see it and that is very important.

Manual one is different, that is probably for more stopping the people who abuse the system and it doesn't work 100% so sometimes you catch people who play fair as well.