Can't Find "All Screens Mode"

I'm running Zoom version 6.4.5 on Windows, and need to be able to view the screenshares of participants in my meetings without them being able to see each others' screens. All my googling leads me to a feature called "All Screens Mode," which is supposed to have a checkbox allowing me to turn on "Allow participants to view shares" - which seems to imply that the default behavior is that participants canNOT view shares.

Yet when I open my meetings, that "All Screens Mode" is nowhere to be found, nor is the checkbox, and the default behavior is that all participants can switch between all shared screens via the tabs at the top of the meetings.

Has this feature been removed? Is it limited to paid licenses? I meet all of the requirements listed on the support article here. . .