But Greenberg said the timing of the incident was irrelevant and imposing the fine, half of which is suspended, shows how seriously the code is taking concussion.
"Today is a line in the sand and shows we're fair dinkum about the policy and how we'll police the policy," Greenberg said.
"It's our view the Bulldogs did not comply with the policy.
"Our view was he should have been taken from the field. The policy is designed to take players and place them in the care of the person most responsible which is the club doctor."
Bulldogs CEO Raelene Castle said while the club was supportive of the league's new concussion policy, it was at odds with the outcome.
"We don't agree with all the findings in the breach notice and, as per the process, will be using the next seven days to have those discussions with the NRL," Castle said in a statement.
A total of 27 players have been taken from the field to undergo the newly-introduced sideline concussion assessments (SCAs) in the season's first five rounds, with 14 of them returning to the field after being cleared of concussion.
Greenberg praised the clubs for the way they've embraced the changes and said player safety is at the forefront of the ruling.
"I genuinely congratulate the clubs for the first five rounds for the way they have adopted the policy," he said.
"We have players taken from the field when historically they wouldn't be."
Five clubs have so far been given "please explain" notices in relation to their compliance.
Greenberg said including the Jackson investigation, three of those cases have now been resolved with the NRL satisfied with responses from Parramatta and Penrith.
Three others are being probed including another involving the Bulldogs and their decision to allow front-rower James Graham to come back on to the field against Melbourne despite looking very groggy.
Greenberg refused to go into detail about the progress of the investigations.
- AAP
