Good question, but I don’t know (yet).
But what puzzles me is how Yoast ‘looks’ at images in the first place.
I know that Yoast checks the featured image of a post or page to see if the so-called ‘alt-text’ has the Focus Keyword in it you’ve set in Yoast’s interface.
But Yoast doesn’t check this with attached images to a post or page, as far as I know.
This means, that if you add images to a post or page with an ACF (repeater) field, these images get attached, but Yoast won’t check them.
I think you should check Yoast’s documentation on this subject.
And if you have found out a way on how to let Yoast look at attached images, I really like to know how you did it.
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