I have my doubts about the use of option mobileLayoutBreakpoint.
I did test it here, click on the 5th thumbnail.

If I use the default value 600 I see on my PC this:

On my iPhone I see this:

But if I use option mobileLayoutBreakpoint: 0, I get better results, on my PC I see this:

And on my iPhone this:

I think the value 0 gives better results as the default value 600, so I propose to change the default to 0 or remove the option.

But I wonder why the image on a PC take 100% of the viewport while on an iPhone there are unused area left and right of the image?

How can I use the full 100% on an iPhone?