Why does Money In not show a deposit balance for an item?

When an item is proposed the deposit balance will reflect in Money In. When the item is then invoiced, the deposit balance will show $0.00 because deposits are only collected on the proposal. 

For example:

Here we have an item that has a 50% deposit requested for both the Subtotal and the Mark Up. Currently, this item is only on a proposal.

Looking at the proposal for this item, the total deposit requested and the deposit balance are showing at the bottom.

Looking at this item via Accounting > Money In for the deposit and filtering for Proposal # 100232, the Deposit Balance reflects 247.50 just like on the proposal's totals.

Now the item is ready to be invoiced. When filtering for the invoice, there is no deposit amount reflected. This is because deposits are solely collected on the proposals.