The only way I kinda “solved” this was using jQuery to check the size of the image (and empty the value of the field if necessary).
A little dirty but it works.
Hope it helps somebody.
I am having the same issue.
I’m using the validation code from here https://www.advancedcustomfields.com/resources/acf-validate_value/ to prevent uploading images < 960px but it blocks every photo even those > 960px