protractor executeScript weirdness with ElementArrayFinder

I have this declared in my Page Object:

this.paginationPageNumberList = element.all(by.repeater("page in pages track by $index"));

Running this inside a function of Page Object, its successful and prints 'no wrap':

browser.executeScript('window.scrollTo(254,1600);');
this.paginationPageNumberList.get(0).then(function() {
    console.log("no wrap");
});

Running the same thing except with a then() gives me an error:

browser.executeScript('window.scrollTo(254,1600);').then(function () {
    this.paginationPageNumberList.get(0).then(function() {
        console.log("wrap");
    });
});

Failed: Cannot call method 'get' of undefined.

Why?