The title of my question may seem misleading; I don't intend to ask how a proper exposure is calculated. I know the exposure triangle of ISO, aperture and shutter speed.
But in several articles I've read something confusing to me; that is a photographer using a light meter is told which aperture to shoot at for a specific exposure.
When I choose an aperture, I take into consideration my desired dof, available light, motion... but mostly DoF is what I think of as my main reason for choosing a particular aperture.
In this video on using lighting and shadows for depth in portraits; Creating Depth, Shape and Form in Portrait Photograph at 25 minutes in the speaker states that he chose an aperture of f/10, I think it was, because the light meter told him so for that particular exposure.
And in this article on high speed sync; "High Speed Sync Flash Understanding High Speed Sync Flash and Shutter Curtains" the author discuses that although his lightmeter suggested to shoot at f/16, he chose to shoot at f/2 to achieve his desired DoF, and this lead to shooting a a shutter speed of 1/5000 and needing HSS...
So my question is both photographers allowed the light meter to chose an aperture for their exposure; this seems backwards to me. Especially in both of the circumstances (portraits), where it seems more intuitive to choose your own aperture and allow the light meter to select your shutter speed for you. Why did they do this the other way around?