The last image always preloads when using lazyLoad === 'anticipated'.

[LeDuc2004]

In the demo https://jsfiddle.net/pmxvunf8/, in slide-2, when I use
$('.slider-2').slick({
infinite: false,
lazyLoad: 'anticipated'
});
the last image is always loaded even though the src has been replaced with data-lazy

[pachylover]

[lazyLoad: 'anticipated'] is a property that gets the before and after images, one for each.