That's what I thought too but it didn't work with the S9 I purchased on BF.
First SIM I put in was Virgin Mobile so I got VM bloatware (My Account, My Benefits, etc.) Factory reset the phone and put original Koodo SIM but VM bloatware still stayed on the phone after factory reset. Hopefully others are having better luck with that.
Either way, dialling *#243203855# on multi-CSC phones will allow the user to change the CSC at ease but I just thought I'd provide the previous information in case they wanted to avoid the hassle of doing it later (changing CSCs factory resets the phone), or if they ended up being unable to change their CSCs.
ebates ebates ebates!