"You’ll create a tulpa by imagining a person in your head, and treating them as a person. The exact mechanism is unknown, but as you give a tulpa attention, and believe it can be a sentient person, it will grow into one, and act independently of you." https://www.tulpa.info/what-is-a-tulpa/
For that matter, you are at a significant advantage in many extremely lucrative professions (notably, politics, management, finance, media, UX design, and law) if you can create an accurate mental simulacrum of the people you interact with. This is basically what separates the people who control what others do vs. those who get controlled.
Here is a study showing the same behavior in Kenya, Malawi, Nepal and the Dominican Republic. I didn't fully read it, but there is argument that such things exist, even if they aren't as prevalent. https://onlinelibrary.wiley.com/doi/pdf/10.1002/ijop.12423
Taylor and her colleagues found that 77 percent of these children said “yes” when asked if they had a pretend friend, and 40 percent spontaneously remarked at some point during the interview that they were talking about a pretend friend. The children offered statements such as, “Her is a fake animal,” “I just made him up in my head,” and “He’s not in real life.” Only one child was adamant that her invisible friend was real.
https://www.psychologytoday.com/gb/blog/growing-friendships/...
(Personal example: I deliberately lied about not understanding how to do long division just so I wouldn't look too clever in front of my peers - I kept up the pretence for several months.)
edit: To directly answer your question: I don't know, and that's part of my point.
Audience. A fake imaginary friend is a prop. The child sees imaginary friends are desirable and performs as if they have one. If there is no audience, there is no imaginary friend.
A bona fide imaginary friend, on the other hand, should be more likely to be addressed when the child thinks they’re alone.