I just read the article. Horribly written. This is absolutely untrue:
Last October, a senior RCMP officer offered an explanation in a letter seen by Global News.
When a Canadian is pardoned, he wrote, the RCMP finds out whether U.S. border officials have looked up the person's criminal file. If they have, the RCMP sends them a notification of the pardon, without saying what the original crime was, and asks them to destroy any records of their own they might have created over the years.
So Global News, one of the most unreliable news sources out there, "saw a letter" but would not actually publish the letter.
In my opinion, ignore this entire article. "Mischief is admissible" was the first clue that there was a misunderstanding of what they allow in and don't. And that immigration lawyer quoted (Global News loves that guy) tells everyone constantly to do a waiver, whether they need one or not. "American Immigration Lawyer" is code for "nothing I am going to tell you in accurate, and I am going to rip you off".