frustratedcanadian said:
BC. I dont think you need to have a valid US visa but must have valid Canadian permits/visa
By definition, one is required to exit Canada and reenter to complete PR landing (unless you are doing it at a CIC office in side Canada).
Flag pole is a term used when you do not enter US and instead just get an "administrative refusal" for entering US and come back to Canada.
Going to US checkpost is still enough proof of exiting Canada.
Hence a visa is not required for flag pole. Even if you have a visa and tell your intention is flagpolling, US TSA would still hand you over a refusal and you would come back to Canada the same way.