There is strange logic in code

[shds86]

When I use ace-diff I'm equaling it with diff-merge by TortoiseSVN or TortoiseGit and I think that the left side is previous version of code and the right side is mine or next version of code. So as I know diff_match_patch provides a method - diff_make(arg1, arg2), which finds difference between arg1 and arg2 which have need added to arg1 for getting arg2. But inside the ace-diff code I find the next lines

const dmp = new DiffMatchPatch();
const val1 = this.editors.left.ace.getSession().getValue();
const val2 = this.editors.right.ace.getSession().getValue();
const diff = dmp.diff_main(val2, val1);

Is It correct to use val2, from ace.right, like "text from", and val1, from ace.left, like "text to"?
Also diff_match_patch provides methods dmp.diff_text1(diffs) and dmp.diff_text2(diffs) the first one returns text from ace.right and the second one returns text from ace.left. It looks like a bug.