An hour a week seems an inordinately long time. My weekly commute, over 5 days, barely comes to that.
That advice is for lockdown (the original one at least) where we weren't allowed to drive without a good reason. In that scenario simply switching the car on will not be enough to start charging the 12v. You have to wait until the ICE comes on which could take a while, especially with the warm weather at the time (in winter it comes on within sixteen seconds to provide cabin heat).
I kept my Corolla fit by taking the longest possible way round to Tesco once a week so I don't know exactly how the car behaves when you just switch it on and wait. I have stopped in a layby and left the car on and the ICE didn't switch on in the time it took me to eat a sandwich and have a drink so 60 minutes might be a reasonable time to have to wait to be sure it eventually fires up. If Toyota didn't bother to have the ICE come on specifically because the 12v was low (a bit naff) then all you can do is wait and if you are whiling the time away reading or talking you could easily not notice when the ICE wakes up so 'wait an hour' could just be Toyota covering their bases.
And I know that one of the issues with the older Jazz is that infrequent use can result in a flat battery (several of my Dad's friends ended up buying solar charges because of it).