The upload path is not set by ACF, it is set by WP. When you upload a file in media that path is the current month. However, if you upload something while editing the post, the path is set to the year and month of the post that you’re editing. The path is not random.
This can be tested by uploading an image and inserting it to the standard content editor in WP. I tried this with the classic editor, however, I’m pretty sure that the new editor works the same way.
