i can see how backtracking would be frustrating for a child, but if they don't miss what they've never had.
the german school system is very rigid and strict. it is not something i agree with at all. They go from something entirely child-led to something entirely teacher-led and there's no inbetween. they go from a fantastic kindergarten with lots of learning being guided through play into this awful school system where they have to copy down texts, do dictation, no project/group work, no playtime or breaktime, the fact that teachers lose it and scream and so on and so on. No art, no music, no sport, no learning is fun activities.
they also pigeonhole the children far too early. Children are sent to different types of secondary schools according to ability as measured by their primary school at about the age of 9 or 10.
If the school estimates that a child is capable of going on to university, they can apply to a Gymnasium which is full-on and intensive.
If not, they go to a Realschule which means they'll train later maybe for something like office work or nursing, something which doesn't require a degree.
If they're not considered likely to manage that, they have to go to Hauptschule which means they can just forget it basically.
So there is a lot of pressure to achieve well at primary school.
School lessons go on til lunchtime then there is a selection of activities that you may choose - but only from one category - so if you choose sport then you do sport 4 afternoons a week and cannot take a music class or a language class - just sport. it would be better if they could pick different things for each afternoon. and this is not compulsory and cos a lof of german mums are sahms most don't stay for the afternoon.
The problem with introducing formal and compulsory learning so early is that some children learn how to fail and are therefore put off learning and school in general at an earlier age whereas if they were to start formal schooling at 6 or 7 they would have already naturally learned both social and academic skills without too much pressure and find things so much easier and see school in a more positive way.
Imo young children learn best when they are left to question things themselves. So if they want to run around and be a penguin then so be it, but then the teacher can then guide that into something productive like "do you know where penguins live, do you know what they eat" etc etc and get them interested in learning that way. i don't see how that can be boring at all.
however if they are soley left to play and never given any guidance then i can see how that would be boring to some.