The lender is interested in getting the highest offer so they can reduce their losses as much as possible. It is quite possible that more than one potential purchasers are interested in buying the house. However, it is the seller’s decision to choose which one to submit to the short sale lender. It is not a necessity that the Realtor submits all offers to the lender because the lender is only interested in the best bid.
The remaining offers can be kept as backup offers in case the original offer doesn't go through. Some lenders require the Realtor to submit all offers, but that is not usually the case. A purchaser may feel that their offer is being withdrawn or withheld from the bank intentionally but there is nothing one can do about it. Think about it. If your offer is not as good as the others, then it would not make any sense for the Realtor to present your offer to the lender. Even if he did present all offers before the lender, it is most likely that the lender will choose the highest offer.