Updating media (screenshots/previews) for multiple platforms without incrementing build

I have an iOS (iPhone/iPad) and a Mac version of my app. When I create a new product page optimization test, on the next page, where it shows Treatment A, I only see the iPhone media there. If I click on "View All Sizes in Media Manager", I can then see the iPad media in the Media Manager. But there are two issues:

(1) There's no Mac media in the Media Manager. So would I need to submit a new build just to update media for Mac?

(2) There's no save button in the Media Manager, and when I return to the product page optimization dashboard, it still only shows iPhone media. Should I presume that any changes to iPad media in the Media Manager are counted in the test and any subsequent application to original product pages?

Updating media (screenshots/previews) for multiple platforms without incrementing build
 
 
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