I'm not quite sure what the above explanation is referring to, since in PA, under the "President" category, there are candidates names (party below)....same with every other categories. We don't vote by line items, we vote by candidate, except in the case of specific issues where a vote is separate.
My understanding was the in general when someone says that third party votes go to another party is simply that they are "taking away" votes from one of the major parties. I hate to be blunt, but it is fairly obvious that a 3rd party candidate isn't going to win. So by voting for them, you are effectively voting against both of the major parties, by not giving them your vote. You are reducing the number of total votes that either candidate can get. In some cases, when a third party candidates platforms are very close to one of the major parties....in the absence of that party, the voter in question would have voted for the other similar major party candidate.