Think of it this way...
When you have one track playing, it just plays along at whatever speed - if it's 0%, it plays at its native speed, but if you pitch it up 10%, it moves 10% faster. Likewise to having two tracks playing, one at 0%, and one at 10% (to match the first); the one that's pitched is not stretching the entire waveform, it's simply moving 10% faster than its base speed, but because they're matched in TEMPO, those beats will align at the play head (the mid point of the screen). This means you'll see the grid for that pitched track moving faster, but still matching at the mid point.
When you SYNC, the master track serves as the target, and the slave stretches the entire grid to match that target grid size. The waveforms march along in a matched stretched display.
And no, without sync, there is no way to stretch the waveforms to match, it just speeds them up or slows them down.