Final edit: We discussed this with the daycare and it turns out our son is a very unreliable reporter - they just ask him whether he wants to go to the toilet or not. Thanks for the help!
Our son is a little over three years old and is not potty trained. We regularly put him on the toilet and he sometimes pees and sometimes does not. He does not indicate when he needs to go yet, so we're just waiting until he starts doing that.
Today, he told us that he is not allowed to poop in his diaper at the (German) daycare where he's been for almost two years now, and that he is only allowed to poop on the potty or toilet. This is all we could get him to tell us and we're a little concerned. We will ask at the daycare whether this is the case or not since our son is not the most reliable witness. We have not heard anything about this from the daycare and they have not shared any potty-training plans or expectations with us.
The whole practice of not allowing a toddler to poop in his diaper seems really weird to me. Before we go in and tell the daycare to let him poop in his diaper, I wanted to ask all of you whether anyone recognizes this as a legitimate potty-training strategy? To me it sounds like a risky strategy to say the least.
Thanks for the help!
EDIT: Thanks for the answers so far! I would also love to hear whether anyone thinks this is a legitimate potty-training strategy or, conversely, whether anyone thinks this is not a good idea.