I can confirm parry instant-casts Power Slash. However it is not related to the strength of previous casted Power Slash.
While this is an interesting trade-off of melee-endangerment, I imagine it is not intended. No need to hit Abrams in the face at the same time as blocking his punch. If it is intended, I certainly fear the repercussions that will come to strength and the rest of the kit in future compensation.
Hoping for parry at first-tick or parry without damage. Glad yamato's right click and 2 work now, hope she doesn't get smacked so soon from a bug.