Other can comment as well but I read that as similar condition discussed for inland spouse sponsorship in that if someone leaves Canada and tries to return but for whatever reason is denied entry then any PR application could be considered abandoned. For this reason with spouse inland applications the recommendation generally is to not leave but how that relates to a close permit not sure.
Maybe would have to assume that the moment you become employed even by the same company in the US that your closed work permit would no longer be valid so you could no longer meet one of the conditions but thats just a personal interpretation. Ultimately the FAQ quoted is a generic statement that applies to any temp resident or even visitor that each entry into the country is subject to assessment by CBSA,no way of course to predict entry or denial.
So guess as your job is moving to the US just have to wait it out and let the PR application move along keeping any returns to Canada to a minimum if at all until you get your COPR. Again all above just personal view and sure that someone on here has been in the same position at some point maybe without an issue