Should I have told these kids to be honest with their parents?

My nieces came over for a few hours today. Five and three. They asked for a popsicle and received one each, because I wasn’t told not to give them any sweets.

Before they ate them, they started talking about how their mom would scold them for eating that popsicle, so they wouldn’t tell her. I suggested to tell their dad instead, and they said that they would do that because their dad wouldn’t mind.

They’re still so young, it feels like having secrets from their mom is not so great. Should I have told them that they need to ask mom first? They did tell dad at pickup, and he was fine with it. They also don’t have a general rule about not eating sweets. They eat cake and popsicles and chocolate when their mom is around. Maybe they were worried because it was close to lunch time, not sure if that would register for young kids. Or some sort of stranger danger thing? I’m no stranger to them, but they don’t often hang out with me without parents, so it might have felt like a weird situation with too much freedom, where they weren’t sure what their parents would allow??