Based on a cursory review, you are correct: if you're timing it with only Jumps, or with Jumps + SSD on cooldown, then they may have well just reduce it by 10s, not 30s.

The only time this changes is if you hold SSD for whatever mechanics reasons, or hold Jumps for mechanics. In these cases, the shorter PS cooldown will result in "less DPS loss" from delaying the Jumps.