Why you dint order it at first place? Good pratice is to get GCMS for first refused application to know Visa officer remarks and exact reason so you can make changes accordingly and then reapply.
Requesting Gcms Notes has no adverse impact. You can request it from IRCC and/or CBSA as well; it costs the same and through CBSA there is a greater chance of receiving it in 30 days vs from IRCC