Firstly your proof was not in the article but the comment section, that premium pay has been abandoned. As for pay rates for Tesco, they are widely available online:
Link to average pay rates:
https://www.glassdoor.co.uk/Hourly-Pay/Tesco-Hourly-Pay-E10250.htm
Pay rates from 2014 handbook:
The pay hits they discuss recently is because some workers are still on double time from pre 2000 and will receive 1.5 instead to make it fair as all other workers receive that. As for night premiums, they are just moving the hours not removing them. The article also mentions considerable hike of pay for younger workers. Considering my link to pay shows averages and it is adjusted by living cost zone, you will find that even a lowly shelf stacker earns a fair amount compared to before.
There really shouldn't even be Sunday premiums. It was introduced before to encourage people to work Sundays when Sunday work was not as common but you will find that people really don't care what day of the week it is now and will clamber to get a Sunday slot for that extra pay. Why offer outdated incentives if they dont need to?