to quote from the post:
One other thing that we are updating is the amount of Defense Tactics available in the Challenger Tier. For this tier, we are reducing the 3 Defense Tactics, to 1 Defense Tactic to better focus the experience and eliminate redundancies. The number of Attack Tactics, however, will not be reduced.
What's really going on:
There are 3 Defence Tactics available on the Challenger Map to choose from, not 1.