Just seeking clarification: when it says The Flash can use Sidestep, HSS, and Flurry, it doesn't mean he can use Flurry with HSS, right?

Thanks in advance.

Compare Quicksilver's wording

Quicksilver can use Hypersonic Speed. When he does he can automatically break away and he can use Flurry as a free action instead of the close attack.

So nope Flash can't use Flurry as part of HSS.

I wish he could. As it stands he can Sidestep/Flurry or Sidestep/HSS.