It means IRCC cannot confirm your NOC with your job duties. Apart from the updated employer job duties, you can add a LOE to explain why are you making the change, Explain politely you wanted to take extra step to provide with the most accurate version. Add distinct bullet points to Explain a few job duties with adding realistic examples/facts. To support those examples, based on your job, You may seek related letter from teammates / manager/ Client that will prove you have actually performed those. You can draft it & ask them to confirm via email or sign. Point is IRCC should get convinced with your the NOC selection & job duties. They will appreciate honesty.
Note - I am not a legal expert, it’s all up to you to decide if you wish you add a LOE.