Schlobbob when I was a sahm and my older two were at Kindergarten and youngest at home, the Kindergarten children did 08:30-12:30.
At our Kindergarten 8:30 - 12:30 are "core hours" when they have a Montessori-esque type curriculum (not that the kids realise) with small and larger group activities and 1:!, the rest of the day is essentially babysitting, although lovely especially in summer as its mostly spent outside.
Only people who need childcare tend to leave children for lunch.
We speak English at home (more rigidly then than now) and DC1's teacher didn't realise she was "the foreign child" until she checked the list (she said). DC1 has never had any non native speaker help or issues (except that she rolls her R oddly, but only teachers notice and say some native speakers do that too). She was only 20 months when we moved here, but only learnt her German at toddlers groups, in the playground, and then at Kindergarten.
I was actually unhappy with the minimum 20 hours thing when we first put her in as I would have liked her to just go 3 days, but actually the routine of going Monday - Friday seemed to work well (for the kids, fewer longer days might be better for parents!) and almost all sahp (we have a couple of sahd) do core hours only and pick up before lunch (which is at 1).
My youngest is enrolled for 7am - 3pm and has to do those hours on my work days, though I don't take him til 8:30 and pick him up at 1 when not working. His German is no better than DC1's was at the same age (i.e. its normal for his age with a few random English words occasionally) and he can't simultaneously translate like DC1 could! :o
He is far tireder than DC1 was pretty much all the time :(