This one just be like when binance disable some account from deposit but leave their withdrawal open reason why binance do that thing then no tell us till date the only thing be say some people they affected why others still they use the exchange, nah one thing about centralized exchange if dem just suspect anything dem fit take action as dem want and still no tell the person reason why dem behave like that.
All these centralized exchanges get some kind dubious ways wey dem dey take dey operate because i see no reason why an exchange cannot give its users information of a sudden change in their platforms, and this is how so many people had lost their coins to exchanges. Even the minimum deposits set by exchanges is another dubious thing because if a user sends an amount that is not up to the minimum deposit, what they should do is to program their system such that the coin can reverse back instead of getting lost in the exchange just because it didn't reach the minimum deposit that is being stipulated by the exchange. So many irregularities have been recorded with exchanges so it's just better to use a wallet that only you can have custody of your coins.
Unless the exchange doesn't mean well for their users, if there is any policy change, they should send mail to their customers or even notifications each time there is a login in the exchange so they will be aware of those changes. It's just that some people don't take these notification signs very seriously.
And for the minimum deposit policy, before you generate a deposit address in an exchange, there is always a warning sign of the minimum deposit, which, as a customer that agrees to obey their terms and conditions, you should obey, but mistakes do occur.
Let's also assume such a kind of mistake happens and you send below the minimum to some exchange. If you contact them, they can help you credit it to your balance manually, but the majority won't do that, either because of the high fee rate for moving the fund out, and for sending it back to the wallet that credited it, that can't be possible unless they will also have to deduct the sending fee from the original amount sent since they won't be willing to cover the fee themselves and take such a loss.