A new one or not, it will not have any impact on the application. The absolutely worst case scenario, they would ask for a new PCC from another country. There cannot be a rejection because again, there is no ground for rejection.
Plus, we are talking about UK certificate here )). Not Russia, not Germany, not France ... UK )) That's one of the countries that shares all of the information with Canada. So, even if he lied about not being in UK and committed the crime after he submitted the application, they will see it and hit him with a nice misrepresentation case.
Anyways, to each their own and every application is accessed on the its own ground. In my case, I submitted an old FBI PCC with a short LoE.