A bit like being a postie, I think the "glamour" of being a supermarket driver is wearing off.
I am currently doing Tesco home delivery shifts, as a part time job in my semi retirement.
I do 2 full days per week, 9am to 7pm. 18 hours paid, with 1 hour break per day unpaid.
I quite enjoy it for the most part, but it can be a hard shift physically. I do my 2 days consecutively and by the end of day 2 I am knackered!
I wouldn't recommend it to anyone who thinks it's going to be a cushy few hours delivering the odd bag of groceries in leafy suburbia. It can be heavy going, and the driving part of it can be stressful too (says an ex HGV 1 driver!). Delivering in narrow streets with zero parking, carrying baskets of groceries up several flights of stairs, trying to find house numbers, running against the clock. If you haven't done multi drop deliveries before then you could be in for a very steep learning curve.
Haven't yet come across this 25 minute van loading thing, maybe that is a local rule. But where I work due to lack of loading bays and too many vans, the loading process does have to be done without any faffing about. And yes a lot of lifting and twisting required. My back is complaining, 6 months in.
So despite having said I quite enjoy it overall, 2 days per week is my limit. And that is from a reasonably fit, soon to be 64 year old.