Lillie I don't think your picture of a nursery class is typical - " I am not a fan of nurseries at the best of times and find it unnatural that 20 toddlers should all have to visit the toilet at the same time after break, all have their snack at an appointed hour, and only be allowed to play with the sand and water when the activity has been set up ....... so heaven help them when they, (especially the struggling ones), are made to sit down and have their language needs addressed."
This regimentation is not what is intended. Professionals with a knowledge of child language development won't "make them sit down and have their language needs addressed" They will provide opportunities for them to speak about what they are playing with at that moment, listen to them, talk to them, play counting games and naming games, all informally. Employing a professional is not the same as employing a ringmaster with a whip and a chair!
All having their snack at the same time? Of course - because if all 20 eat their snack at a different time, they will want to join the others who are playing, and carrying food around everywhere is not a good thing. Families have got out of the habilt of eating together, but it is an important part of socialisation, and a moment to sit quietly all together. In the nursery I used to run, we spent the time as everyone was gathering for snack time in talking together, and singing nursery rhymes and songs - all things which help prepare them for reading without seeming like "lessons".
After the snack, the toilet and the handwashing. Did you know that the human elimination system is stimulated by eating, and after 20 minutes, a toilet visit is signalled by the innards? Taking one child to the toilet occupies a helper for several minutes, leaving the rest with one attendant fewer. Taking 20 of them, one after the other, could keep her out of the playroom for an hour. Taking them all at the same time means that they are "processed" in one "go" (to use a relevant word) and the helper can then return with them to the main room to join in supervising everyone. This doesn't mean that they are regimented and have to perform, or that no-one can "go" at any other time.
The sand and water are usually set up at the start of the day and stay there. Why waste time setting it up after the children are all in the room ?