To make this decision which will allow you to purchase the property on the agreed terms all banks do require that you have the cash to close, whether in the form of proof of cash in the bank or a pre-qualification lender from an approved lender.
If you really want to purchase a property in a short sale and are satisfied with the price and terms negotiated it is greatly to your advantage to prove that you have the funds to back up the offer you have made. They will take your offer much more seriously if you do and this sometimes means you can negotiate a better deal.
On the other hand there is no need to disclose more than the amount necessary to close the transaction so I would ask your bank to provide proof of funds for only the amount offered.
Thanks again for your reconfirmation
It is never fair, but the banks hold all the cards & all the power. If you do not want to play their little games, they will never give you what you want. It is really that simple. They can, and will ask for anything they want.