"There have occasionally been reported cases of people being refused entry back into Canada. Remember, the US immigration authorities have also refused you entry if you did not have a US visa or you just came to flagpole, so you may be caught in a no-man’s-land.
You could have problems in the future. For example, you will have to declare every time you re-enter the U.S., at all later dates, that you have been refused entry previously to the USA. It will be in their databases once you flagpole. There is nothing you can do to avoid this if you flagpole unless you actually plan a full trip to the US. We suggest going out for dinner or going shopping. It is best to stay over night if you can. (This is all provided that you have a valid visa to the US, of course.)"
https://www.immigroup.com/news/flagpoling-your-way-new-work-or-study-permit-or-permanent-residence
I am a bit worried about this since I don't have US visa and plan to do flag pole, anyone's got a second opinion on this one?