No, sir. The people who are supplying you that information are incorrect.
The screening that goes on for a person who has a POL is exactly that for a person who has a PAL. At the time of renewal, they go through the same rigorous background checks as a person with a PAL. They've been doing so since 2001, which was the final date that you could obtain a POL. For the last 14 years, people who hold POL licences have gone through the same background check as a person who has a PAL at the time of renewal. If those people who have been in lawful possession since that time don't pass the background check, which is the same as with the PAL, they wouldn't have a licence.