I assume maybe the other one is to align more closely with Argentina or something? If you look at the time zone map, they just as easily could have had the whole mainland country on one timezone. Bolivia, Paraguay, and parts of Brazil share the same timezone as the northern part of Chili and are just as far east as the southern parts of Chili.

Easter Island makes sense, you don't necessarily expect islands that are far away to share the mainlands timezone. Antarctica is one that probably catches a lot of people since most time zone maps don't even bother to include it and there is no real population there.