YANBU to be concerned.
But as others have said, it's very rare!
My dd goes to nursery 3 days a week. For no other reason than "she can".
She gets the 15 hours free thing.
She loves it there. She happily runs in and hangs her coat up. I am lucky if I get a kiss goodbye!
I think the nursery children are a good indicator of the nursery.
Kids will not pretend to be happy!
Kids will not gladly run to a place where they are getting hurt.
Go and visit some nurseries. Explain your concerns. You won't be the first.
Without being a creepy stalker, watch the children for a bit. Are there several interesting activities out for them to be playing with? Are the kids playing with them?
Are there enough adults with each group of kids?
It was hard for me to let dd start nursery. She has a food allergy. She has co-ordination delay. Her speech is unclear. (Sorry dd, I love you to bits!)
But she loves it there. She goes and hugs the staff.
Every nursery in the country will be concerned after seeing that news. 99.9% of them are innocent.