First off, recognize that 'stage' is a defined term in NBC.
"Stage means a space that is designed primarily for theatrical performances with provision for quick change scenery and overhead lighting, including environmental control for a wide range of lighting and sound effects and that is traditionally, but not necessarily, separated from the audience by a proscenium wall and curtain opening."
As noted, the edge of stages is exempt from guards (and tactile elements under 3.3.1.19 - NBC 2020)
Secondly a stage has its own unique Code requirements, including sprinklers, deluge sprinklers for the stage area, fire curtains, ventilation and the like. (3.3.2.14 in NBC 2020).
I went through this stuff with someone in our area who was contemplating renovating a church to create an arts centre and theatre. It stuck in my head ...