You've described an example where the addition of a third candidate causes a voter to strategically change who they're going to vote for, based on the expected

You've described an example where the addition of a third candidate causes a voter to strategically change who they're going to vote for, based on the expected outcomes under a particular voting system. That's not the same thing as the voter's actual preferences changing, it's just a manifestation of a limitation of a particular voting system.