Hi Felix,

Yes, from bitter experience I've also found it's not always a good thing to rely on Wikipedia! Fortunately other sources exist here. Here's an article from 2019 written by someone aboard the CCGS John A. MacDonald:
https://maritime-executive.com/editorials/photos-through-the-north-west-passage-with-the-manhattan-in-1969

In it he states the presence of Canadian vessels was a diplomatic solution for prompt response to any leaks of oil in the passage, and that the Manhattan's long/straight hull meant ice could grab the ship, and that its astern power wasn't sufficient to withdraw. As a result the ship required icebreaker assistance to undertake the voyage. He also writes of the Macdonald's travails during the voyage and his stomach's response!

A second report written in 2008 by the project manager for ESSO is available here:
https://www.pame.is/images/03_Projects/AMSA/AMSA_Background_Research_Docs/History_and_Governance_of_Arctic_Shipping/2-3-The-MANHATTAN-Story.pdf

This author was aboard Manhattan and wrote about Canadian icebreaker assistance, with Canadian staff aboard Manhattan itself, and reports Manhattan 'often got stuck' because of limited stern power and had to be assisted by the Canadian ships. Two US icebreakers were there but (as they were smaller) they were not useful for the project.

These are two (among many) references which note the Manhattan got stuck and that the Canadian icebreakers were necessary to release Manhattan and allow the trial to continue. They are written by people who were aboard the participating vessels, so are of great interest for anyone interested in the project!

Simon