I feel for the staff that will be expected to work longer hours on the one day they are used to having shorter hours.
I used to work in retail - this wouldn’t have an impact on my working hours at the time. Remember that retail staff generally work by the hour with a cap at 37.5-40 hours; only managers are salaried, they would be the only ones expected to have a longer working week.
Retail staff don’t specifically work when the store opens until the store closes, shifts are staggered eg one person works 7-3, their colleague works 9-5 etc. They can start work before the store is open or stay an hour or 2 after it closes - so even before this change retail staff could still be asked for a full 9 hour shift on Sunday.
Personally I was a poor uni student at the time and wouldn’t have minded being able to work later shifts on Sunday, or the extra opportunity for overtime. I used to have to get taxis to work to start at 7am on Sunday because public transport wasn’t even running.