i might have something to add here. Imagine these high gravity regions as a wave in the ocean. The wave is "powered" by physics, so additional propulsion is not needed. The comparison between gravity and time can be water and light respectively. If you are riding the front of a massive wave then the light is dimmed greatly by the surrounding wall of water, effectively reducing "sunburn" or relative aging. So by riding these gravity waves you can reduce mechanical propulsion, seemingly reduce aging, and reach the destination in a more timely fashion. Sound about right?

There are many ways to travel and time dilation would make more sense when parallel realities are more understood, here are infinite earths so technically we could travel to ourselves in any point of our evolution. I can share an even faster method though :) Resonance Shifts all points in space are different locations, therefore a quarter at location A is NOT THE SAME QUARTER as a quarter in location B if you bombard the A quarter with the B quarters resonant frequency, the A quarter will have to instantly teleport to where B is this is why people have described materializations and dematerializations. nasa footage of ufos blinking in and out is abundant. Montauk project members experience dimensional shifting through resonant bombardment Philadelphia experiment is another crude example. good day :)