What do the conditions of SWR's Delay Repay scheme actually say? For a return ticket, compensation is related to the length of delay. The question is whether delays on outward and return journeys are treated separately, as they are when calculating the minimum compensation payable according to NRCoT, or in aggregate.
As long as SWR's scheme pays no less compensation than the minimum set out in NRCoT, it can relate compensation the the aggregate delay. The idea would be to benefit a customer who, say, had suffered a delay of 50 mins on their outward journey and 80 mins on their return, so maybe that was the intention.
On the other hand, if the intention was to compensate customers by more than 100% of the cost for very long delays, something seems to have gone wrong in relation to those purchasing out and back singles, who are only entitled to a maximum of 100% of the total cost of both tickets.
My suspicion is that SWR intended that their scheme would calculate compensation based on the aggregate delay. Whether the way it is worded makes that clear is another matter entirely.