Because games use different terminology than real life does. You don’t seem to have a problem with the terms used in BW, even though they aren’t used the way they are in real life.
You would be wrong. What I know is that you’ve played RPGs for a while, post to a forum wherein multiple types of games are discussed, and are fluent in English. My only assumptions are that you know we’re using bypass as a verb and not a noun, and that you’ve paid at least a modicum of attention to games outside your preferred systems.
There are encounters. Sometimes, for any number of reasons, players deliberately avoid them. Those are bypassed encounters. If you, when running BW or TB, say there are signs of orcs in the east and the players say “I don’t wanna fight them, let’s go west,” they have bypassed an encounter.