Is this canon?

Since it's Dark Disciple?

https://youtu.be/7d6-2Sye7Vo?t=2m38s

Are spool episodes canon? If not all, which ones?

The video you linked isn't, but Bad Batch (the one with Padme on the ship) and the Utapau arcs are.

Why didn't dooku do that against the pirates?

Because TCW has it's head up it's own arse.

In the novel he loses anyway. 🙂

Originally posted by Beniboybling
In the novel he loses anyway. 🙂