The one who hops into the rocket and leaves, has to accelerate (to gain speed).
Because one frame experienced the acceleration, and the other frame didn't, the frames are not symmetrical.
The U-turn is not the only element that requires acceleration (and deceleration upon landing)
The paradox itself was not that the twin's experiences are different, rather than the one who traveled more, aged less.
At least, this is what I remember from my university years.
peselev t1_j8esdxt wrote
Reply to In the twin paradox, what happens if the travelling twin never U-turn to get back to earth? (explanation in the post) by PoufPoal
The one who hops into the rocket and leaves, has to accelerate (to gain speed). Because one frame experienced the acceleration, and the other frame didn't, the frames are not symmetrical. The U-turn is not the only element that requires acceleration (and deceleration upon landing)
The paradox itself was not that the twin's experiences are different, rather than the one who traveled more, aged less.
At least, this is what I remember from my university years.