Hi Christopher,
Thanks for reaching out.
The adding the lazy loading attribute on the images instructs the browser to do what they seem fit. So it is your visitors browser that has the logic to lazy load or not.
When ochResponsiveImages processes the page it doesn't see the page as it is rendered, but it sees HTML code. So there is no way to determine if an image is above or below the fold. next to that, the fold differs on the visitor his device: a mobile device in portait has a different 'fold' then a desktop.
So the only thing we can do here is turn them all on, or all off.
I do not think this is an issue as the browser probably evolved to solve this use case in the best way: when the browser renders the page, it actually knows where the fold is and starts loading first the images that are above the fold (lazy or not). So I do not think adding lazy load will impact the largest contentfull paint, and if it does then the benefit of not loading the images not above the fold outweigh the 'cost'.
Again, this is what I think and what makes sense to me... not saying this is technical correct reasoning as I haven't found any information on this.
regards,
Ruud