If you are moving from point A to point B and you pause in the middle - You actually did not reach the end of your tween. If you press start again you will continue previous motion until you reach the end. In this case "Start tween" works like a "Resume current tween".
While stopping the tween will mark your current position as the end position. Pressing Start should not do anything until you set new target.
Don't know... maybe I'm overthinking this.
And one more expression could be useful - "Current time". To return how many time, in seconds have passed from start of the tween. For example if your tween duration is set to 7 seconds. It will return value between 0 (start of the tween) and 7 (end of tween)
This could be a nice addition to stack things up. Or do something else at very specific time of the tween.
Sorry for all this requests (moaning about) but this plugin is so nice and so simple to use. I've been using it for last few days and it saves me already a lot of time.