Dwarves are famously "Slow but Steady":
Slow but Steady
Dwarves have a land speed of 20 feet, which is never modified when they are encumbered or wearing heavy armor...
Increased gravity on worlds will double (or more) the weight of characters and their equiptment:
High Gravity
On high-gravity worlds, characters are burdened by their increased weight, and their physical abilities are affected accordingly. On a high-gravity world, where the gravity is at least twice as strong as standard gravity, a character (and her gear) weighs twice as much as on a standard-gravity world, but she has the same amount of strength. Such characters move at half speed, can jump only half as high or as far, and can lift only half as much...
My question: Does it make sense for dwarves to retain their 20ft move speed in high gravity? Other impacts of high gravity would remain, but maybe those sturdy dwarves would power through the gravity's effect on movement.
As written, it seems (to me) that dwarves suffer movement penalties just like anyone. I just think it would be cool and fun for their movement to not be hindered. I'm curious what others think, though.
I think the way it's written, non-dwarves are getting double whammied. Not onlyy are their bodies heavier, causing the half speed. But their gear is heavier too, which might cause some issues as well for the less physically strong.
I think you're understanding the RAW interpretation. I don't see any fluff problem with letting Dwarves keep their 20ft speed, though it would be a houserule.