Using Grey's example above, even without tweening, if you adjust a position like that after overlapping collision, the object moves a lesser distance for that update (just imagine object moving at 500 pixels per second, being 1 pixel away from collsion, and it overlaps the collision boundary by 499 pixels in next single update, you adjust the object, and it end up moving only 1 pixel for that update). Reason you don't notice that object moving slower in that last tick is usually because the update frequency is high enough not to notice, and you don't penetrate by such high distances. If you want an accurate collision response, with variable velocity, at extremely low frequencies, it's a bit extra work no mater if you're tweening or not. With tweening you just have to sometime adjust old values again to correct some situations (like object leaving screen from one side and entering from another).
My code sample isn't showing an overlapping collision, it's showing a bounce, thus it has still moved 100 pixels (just split between two directions). How could you deal with that in tweening? The tweening would need to know also about the bouncing (i.e the altered path of the object) in order to calculate the correct placement for the object.