https://www.metv.com/stories/jean-stapleton-considered-herself-an-introvert

Offstage, she was much more reserved.

https://www.metv.com/stories/jean-stapleton-considered-herself-an-introvert

Offstage, she was much more reserved.

Oh, those MeTV articles! At no time did Stapleton say she was an introvert, this is the quote from the article itself:

"I don't think I'm even an extrovert," she said. "I'm rather reserved. It's true of a lot of actors. They put on a cloak when they go on stage and that's why they enjoy it so much".

She's obviously comparing herself to other stars/celebrities. These people all have outgoing personalities compared to the average person, if they didn't they wouldn't be able to perform in public.

It's possible. Just as there are millions of ISFP singers and musicians who learn to perform in public, the same could be true of actors.