The date should show the date of the last payment.
The paid feature is quite simple in the moment you understand it. When you use something like paypal it is not so obvious. But assume you want to provide "payment on invoice" ( I dont know the english term).
Our orderstati follow the law, the legal system.
A "Pending" order means that the shopper selected the wares. Imagine you would sell rare tickets for a concert, a pending order means, the customer has them in his hand and is going to the cashdesk.
A "confirmed by shopper" order status means, that the shopper confirmed to the contract to buy the wares. According to german law there is no contract yet, just the shopper "signed" it.
A "confirmed" order means, that the vendor agreed to the agreement of the shopper. Now we have a real contract. Depending on your TOS, the contract could already exist, when the shopper agrees (depends also on your country laws).
So now you see yourself, nothing is told about being paid. So the next order status is usually "shipped". That works, when you use something like paypal. You just let Paypal set the order to confirm. So when it is confirmed, it is usually also paid. But that is just a mindset thing.
When we use other payments for example by invoice, then we get
Pending, confirmed by shopper, shipped.
Shops can rearrange their orderstati and add extra orderstati and so on. But most time it is hard to fullfill both systems in one shop.
With the paid feature it becomes easy. You can set an already shipped order to "paid", when it arrives on the bank. Or you can still use it with paypal. Paid is not just a boolean, it keeps the "paid amount".
When you have todo a partial refund, vm creates now the "credit note" for you. The credit is in the balance ;-). You can directly see how much you have to refund. In future there should be also an extra update by paypal, when you do a refund, so that it lowers the paid and the balance should be correct again.
It can be also used later for "recurring payments", "installments" and so on. Also the bookkeepers may like it. When it works, then the bookkeepers sees always the finally paid amount.
I should add that to a docs somewhere.