Three things:
1) Bullet Dance is bugged in reference to the time mod, you actually fire 50% faster with only one level of TH, and normal speed with TH 2. Although both TH and MBD bonuses do not stack, no.
2) This means you can fire more shots with the GCB on single fire, as TH alone doesn't effect it on single fire mode.
3) Storm bolter pistol shouldn't be affected by TH, but it is, and this is also a bug.
But no, TH bonuses + MBD don't mean double extra shots for rapid fire pistols.