That is because not all of the tracks are set to snap to a musical timebase. For instance, if you have one audio track that has not had its tempo defined, it will fall out of time with those that have, as well as any MIDI - as time is one of the main things retained.

Linear timebase is just that linear so if you bend the time of the other tracks the linear one retains its tempo structure, only preserving the same start point, as that is the only thing that has been defined.