I don't think it is "time travel" any more than other means actually available* to some small extent now that slow one's rate of aging as measured by clocks on earth. Yes conceptually it is possible by accelerating for a few years at the few Gs max the body can tolerate for more than an hour, so you could in principle live to die 200 years by earth's clocks after your birth, but actually being the "traveling twin" to do that probable would cost more than a year of the world's total GDP, so will not be done, even if technically possible.
Much more probable of actually being done is learning the detail of how bears do hibernate for many months and some of that knowledge being applied to humans so they can live to see their great, great grand children and the nature of the world that will exist then. Or an application of that knowledge may be government financed to reduce the food and other cost of colonizing Mars, etc.
In both cases no one is Traveling into a future that does not yet exist. We all are Traveling into future as it becomes the present. But via space ships or suspended animation, one can live longer or "age more slowly" by Earth's clocks.
I have asked you before if you call suspended animation "time travel" - no reply yet, but I'll wait. There is no logical or rational reason I can see /understand why only one of these two methods of slowing the aging process should be called "time travel" and not the other. If you can tell me one, please do.
It is not that the laws of physics do not prohibit time travel (or dozen of the other concepts in science fiction) - it is the simple fact that there is no where to travel too as neither the future or the past exists ANYWHERE now. One once did and the other some day will be our "now." The laws of physics do not prohibit travel to the apex of a sphere. - What prohibits that is that there is nowhere an apex of a sphere to travel to.
* The drugs inducing coma and lowering whole body temperature as used mainly with brain and open heart replacement surgery, which takes most of a day to do.