It’s a great phrase and describes pretty well what it’s like when our loved ones rise to an occasion. They will interact with old friends as they might have before their disease came into our lives.
I am not sure it’s really play acting as the term implies, however.
I think it is a way for our loves to meet an old self. Somewhere in there is the person he was before the dementia. He [or she] has an awareness of that persona; social settings offer an opportunity to bring back some of who she [or he] was.
You’ve set the stage for that persona to come forward and shine. It’s a huge effort. It exhausts most of our beloved ones so much that they need a few days for a recovery.
My theory is just a poetical stab at describing the magic of showtime, especially for anyone who is seeing it for the first time. No science.
this is our life 