In theory that is what is happening, but in RAW terms it means that in the caddy corner case where a person with 1 IP goes first charges across the room and kills runner C but is cut down in the 2nd IP in the middle of the room. Movement rules during combat were a little bit of an oversight that probably should have been corrected in SR4A. Generall they make sense, but this one issue still bothers me.
One advantage is that it keeps low IP players engeged in combat since they still do something (move) during the entire combat turn. It also allows everyone to run, sprint or walk in the different IP's. Also they reduced the movement rate to where the person is not an olympic class athelete.