Describe the bug
Players on grappling hooks are not affected by different levels of gravity on other Advanced Rocketry planets

Version
grappling_hook_mod-1.12.2-v13,
AdvancedRocketry-1.12.2-2.0.0-13,
Minecraft Version 1.12.2
Forge 14.23.5.2860

To Reproduce
If you can, steps to reproduce the behavior, e.g.:

1. Teleport to another planet with low gravity (/advRocketry goto dimID)
2. Use grappling hook
3. Player will fall at same speed as on overworld
4. See error

Additional context
Tested primarily with Advanced Rocketry, however, I also tested Galacticraft and Valkyrian Skies.

Wasn't sure whether this counts as an incompatibility, or a bug.