SDP during temporary absence of partner

My client was overpaid SDP because he failed to inform DWP that his (non-recourse) to public fund wife had come to live with him.
During the overpayment period, she was actually out of the country caring for a relative, for a period of 32 weeks and 2 days.

Is there any argument that he was not overpaid during all or some of the period of her absence?

As they would still be considered a couple as absence was temporary and not expected to exceed 52 weeks, I suppose he would have had a ‘partner’ for para 13 Sched 2 IS regs even during her absence (acc to definition in reg 2)?

But this does not really sit well with what it says in S&M commentary p 625 about thes assumption that partner cares for disabled claimant (which does not apply during her absence).  And if he could have received benefit at couple rate, would this not have stopped after she had been gone for 26 weeks, which implies that something in the household after 26 weeks, even if they are still a couple.