Sorry, I can't read the seekingalpha article b/c of the paywall.
I'm assuming (based on my general understanding of retail, not from having read SHLDs annual report) that not every location is losing money. Some must be profitable and others losing money, but on average the whole is losing money. Since they've been handing back store leases for almost 3 years now, they must be handing back the ones that are losing the most and holding onto the ones that are profitable or could be turned around.
I'm not an expert but my understanding is that in bankruptcy the judge can decide which executory (contracts in which both sides have to perform, like a lease, as opposed to debt where only one side has to perform) contracts to keep and which to discharge. If they do away with the master lease completely, they would lose the remaining profitable stores, the rights to sublet some of the valuable leases that they don't give back and the right to get paid if SRG wants to take back a lease that SHLD didn't want to give up. So, for instance, if SHLD gave SRG back half the square footage of a giant box and SRG paid to redevelop it, the remaining half is worth a lot more if you can assign the lease to a 3rd party.
If SRG had individual leases for the properties, I think it would look a lot different, but if it's all under the master lease and the options are take it all or leave it all, then I think SHLD has some strong incentives to hold onto it or to use the threat of cancelling to renegotiate. But they can't have it both ways, if they want to stay in the properties, then the master lease has to be accepted. It's still too early to guess how this will play out.