The determination on a checked swing requires the umpire to ask himself one simple question:
Did the batter attempt to hit the pitch?
If she did, it's a strike. If she didn't, it's not.
There's no playing rule that says "if the bat went so far" or "if the batter rolled her wrists" or "if the bat broke the plane of the plate" that it automatically equals a strike. The "offer" is strictly at the discretion of the umpire's judgment.
There are general
guidelines offered to umpires, in manuals and training, to aid them in making the determination of if the batter swung or not and things like the batter "breaking her wrists" might be one of those guidelines. But they are just that- guidelines- not actual playing rules. The determination of a swing is still left up to the judgment of the individual umpire observing it.
Here is what the ASA Rules Supplement has to say on the subject:
CHECK SWING / BUNT STRIKE.
Normally, there are four areas which constitute whether or not a batter
swung at the pitched ball or checked their swing.
A. Did the batter roll their wrists?
B. Did the batter swing through the ball and bring back the bat, unless
the batter draws the bat back before the pitch arrives?
C. Was the bat out in front of the body?
D. Did the batter make an attempt to hit the pitch?
On a bunt attempt where the batter puts the bat across the plate and
the pitched ball is out of the strike zone, a ball should be called unless the
batter moves the bat toward the ball.
In each of the above situations, the umpire should think in terms of priorities.
First, was the pitch in the strike zone? If so, it is simply a strike. Second,
did the batter swing at the pitched ball, or, in the case of a bunt attempt,
did the batter move the bat toward the pitched ball? In either case, it is the
plate umpire's call. If in doubt, or if blocked out, the umpire should call the
pitch a ball. If the umpire calls the pitch a ball and the catcher requests the
umpire to go for help, the plate umpire should ONLY ask for help if there
is doubt in their mind as to whether or not the batter swung at the pitched
ball. On a missed bunt attempt with two strikes, the dropped third strike rule applies.