The difference between a democracy and an authoritarian nationalist state is the commitment to truth. The pretext that the descendants should be shielded is actually very very toxic. It is precisely what Germany has very honourably refused to do. People should know the truth about their ancestors. This applies to descendants of victims and to descendants of criminals equally.

If there is an actual reason to not do this right now, the government should give a different but short timeline. They could say that they will keep the records secret for 2 more years for example. We can then argue about the timeline, but the underlying principle holds: in a democracy the truth should come out.

That said, I am not convinced a shallow propaganda victory like this even matters. There is nothing new the putinist state would actually be able to say that it hasn't already.

Edit: and in fact, by keeping the records secret, the putinist propaganda machine wins even more, because they can (a) say whatever they want about the content of the secret files (b) can say whatever they want about the extent of the files, and (c) can claim that the Canadian government is complicit in covering up for Nazis. Keeping the records secret gives control of the narrative to Putin hands down.