I don't think there's anything wrong with it. As Evie says, maybe they're expecting some/most of the kids to have a proper dinner when they get home, so are only giving them a little 'tea' in the afternoon.
And there's nothing really *that* bad about jam or honey sandwiches, is there? When we lived in the Netherlands, kids only had peanut butter, jam, or cheese sandwiches at nursery. NEVER did they have hot food for any of their meals. Dutch kids are a heck of a lot healthier than ours, so if they get enough time outside to run it off, then no problem.
Fwiw, when my oldest was at nursery, it bugged me that she had a full meal at 4:30 in the afternoon. I then had a proper dinner with my husband and my youngest, and she was left to have a snack, as there was no way she was making it to bedtime without something else to eat. So, as far as our meal preferences and schedule are concerned, I'd be quite happy with a little something in the afternoon and then we can all eat together when we're home.