thank you, so it means the WL will be CO or not will only be known after PSLE result out or earlier?( after the exercise preference stage?)

dear parents one quick question, my son applied to only 1 school under DSA sports O level track and got waiting list, it seems in Oct there is a exercise school preference. If he choose this 1 WL school only, and if his PSLE get unexpected good enough result for IP program, can I choose another IP school even thought he exercise the preference for the WL school? Tks!!