I think the distinction is that in Golda's Balcony and IAMOW, the solo performer was playing someone other than themselves in a play with fixed and structured text. Crystal, Whoopi, Cantone, and Dame Edna all had shows that were more improvisational and closer to stand-up routines than actual plays. Also, actors other than Feldshuh and Mays could and will play those roles in the future, which makes a strong argument that those shows were "plays" and not "events." No one but Crystal, Whoopi, Cantone and Dame Edna could ever do their shows.
Primo is a play that Anthony Sher developed in close connection with the Levi estate. While other actors certainly could play the role, the estate only trusts Sher and won't, at this point license it to be done by anyone else. That aside, I think it will be deemed a play for Tony purposes.
"What a story........ everything but the bloodhounds snappin' at her rear end." -- Birdie
[http://margochanning.broadwayworld.com/]
"The Devil Be Hittin' Me" -- Whitney