One of several fresh tweaks introduced this year, the rule stipulates rucks cannot cross the centre line at ball-ups before engaging with their opponent.
Swans star Grundy found a loophole on Thursday, shaping to jump before stopping and luring GWS opponent Nick Madden across the line to win a free kick.
AFL general manager of football Greg Swann admitted the AFL had not anticipated such a ploy and was "glad" Grundy did it during a practice match, rather than in the home-and-away season.
"That's an interesting one. We will have a chat about that one," Swann told SEN on Friday.
"Our overarching thing is for people to jump at the footy, so if you don't jump at the footy, what does that mean?
"But if you're looking at the letter of the law, he didn't do anything wrong either.
"It's probably one we didn't contemplate, but anyway, we'll have a look at it and see where we go."
The new ruck rule had already been in the spotlight, following multiple incidents in the Carlton-Geelong practice match on Wednesday.
Cats big man Shannon Neale was lucky to avoid serious injury in a collision with Blues opponent Marc Pittonet.
Pittonet also had a free kick incorrectly paid against him when he stepped around Sam De Koning's mistimed jump to take possession of the ball.
On Thursday, the AFL clarified play should have been allowed to continue.
Eight-time All-Australian Max Gawn has been a vocal critic of the ruck rule, fearing it could lead to predictable contests that favour athletes over footballers.
Swann admitted there has been "a bit of controversy" around the ruck rule but insisted feedback from clubs has been positive.
"It seems to be on our data that there's more scores out of centre bounce too because the guys that can get up and palm it properly are hitting their mids on the fly and they're getting the ball out a lot cleaner than perhaps they were last year," Swann said.
"There's a whole lot of things that come with it if we can implement it properly."
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