Well I didn't know it was called that at the time. If I recall, a book, perhaps Alice in Quantumland, or some other similar book named the idea for me eventually. I also didn't know how what oxygen was called, once upon a time, and somehow managed to breathe.
Anyway, I feel grateful to my parents that they managed to feed imagination without deceit, and I also appreciated that gifts came from my parents, some requested, some unbidden and all with love.
You said "I thought everyone was just playing up to the same fun thought-experiment" which implies you did that thinking at the time. I'm not questioning whether you knew how to breathe or understood the mechanics of it. I can only go by the information you provided.
Your reply even shows you don't understand the magic of Christmas that some children felt.
> I feel grateful to my parents that they managed to feed imagination without deceit
You're framing this deceit as a bad thing. What do you think about parents pretending a child's spoon is an airplane?
Anyway, I feel grateful to my parents that they managed to feed imagination without deceit, and I also appreciated that gifts came from my parents, some requested, some unbidden and all with love.