For example most people just wake up and go to work in the morning, but in the evening they meet friends, BBQ, hike/run through nature, do sports etc., and prefer doing those activities while it's bright outside.
The question in these polls had been which time the person would prefer. A big majority in Germany chose "summer time". So without any reasons given/discussed/researched the preference is summer time.
Of course there are proponents with reasons for or against this or that time but this doesn't matter as the majority does not decide by reasons.
My point is that alone the naming the time "summer" or "winter" influences the preference to a big extent.
"hurr durr summer better than winter, me choosey summer"
There were say some 100s of people called by phone, asked a lot of questions about a lot of topics, one of them is "which do you prefer: summer or winter time" - I would have said summer (without thinking to much) because I like the long summer evenings too.
That has nothing to do with misunderstanding the question.
It is of course possible that the average interviewee is well prepared or thinks long and hard before answering without letting the wording influence their answer.
But you should at least consider the possibility that also the german naming (summer/winter) could influence some people (like me) in their answers.
(I think the wording can have a big influence (maybe because of my linguistic background) but you are free to disagree)
And if we are permanently moving our clocks to advance by an hour, why stop at just one hour? Why not have +2h or +3h so we get even more brighter evenings.