Canny Tumble Questions

[Artificial 20]

Canny Tumble:

When you use Acrobatics to move through an opponent's threatened area or space without provoking an attack of opportunity from that opponent, you gain a +2 circumstance bonus on your next melee attack roll against that opponent and that opponent is denied its Dexterity bonus to AC, as long as you make that attack before the start of your next turn.

Link.

Main Question: Does this work simply for attempting to avoid the AOO, or do you have to succeed in the acrobatics check to gain the feat benefits?

Follow-Up Question: Can a clever opponent avoid triggering this, such as by using total defence, or simply declining to use their AOO at the time?

[Fuzzy-Wuzzy]

You have to succeed.

No, because you use Acrobatics to avoid provoking, not to avoid an actual AoO.

[Artificial 20]

Fuzzy-Wuzzy: That seems to create some strange rules interactions, though:

Threatened Squares wrote:

You threaten all squares into which you can make a melee attack, even when it is not your turn. Generally, that means everything in all squares adjacent to your space (including diagonally). An enemy that takes certain actions while in a threatened square provokes an attack of opportunity from you. If you're unarmed, you don't normally threaten any squares and thus can't make attacks of opportunity.

Wouldn't that mean a character could negate the effect by sheathing their weapon at the end of their turn? And that arming themselves would counter-intuitively make them more vulnerable? To say nothing about reach weapons.

[Fuzzy-Wuzzy]

Drawing (without Quick Draw) or sheathing takes a move action, so they'd screw themselves badly if they insisted on doing both each round just to deny you Canny Tumble.

Yes, the interactions are non-intuitive. That's why I dislike all the feats that give you a cookie for getting hit or avoiding getting hit or whatever. They are flavorful, yet goofy.