I cannot find anywhere in the Starfinder Core Rulebook that states Small creatures move at 20ft instead of 30ft during combat. There is nothing listed under the Race chapter for Ysoki that says they move slower than medium size creatures either. I know Pathfinder has general rules for Small vs. Medium size, but I'd like to see the specific rule.
Otherwise, it says on page 17 of character creation that all characters move 30ft.
Later in Tactical Rules Pages 255-256 there are no special notations indicated that small creatures move slower.
Lastly, in the legacy conversion section starting on page 500 the only race with a movement hindrance is dwarves who have their expected 20ft of movement. Gnomes and Halflings just say "small" and there is no reference to their movement.
Thoughts?