Hi El,
Yes, it would be logical to expect that if the -s can be given ;pgport=5433 in the prerequisite check operation it should be able to consume it in the install operation. I can reproduce your error, and logged a bug for it. We will be addressing it in SP3, sometime in the fall.
Sorry for the inconvenience, you can work around this issue by setting an environment variable called PGPORT and assigning it a value of 5433.
Sincerely,
Kasia