I *think* -- and mods will weigh in if I'm wrong -- the CRA DIDN'T do any validation in the first place, which is why you're now asking full DV from CA.
The CRA only does a *verification* which is a process a toddler with two sippy cups and a dirty diaper could manage, as it really only involves one computer talking to another. It just makes sure the SSN, DOB, NAME and ADDRESS match up. And if you're named ivyalmighty, NONE of those have to match as long as the ADDRESS is MOSTLY the same....
What you wrote to the CA requesting is a debt VERIFICATION, which is a request for lots of slightly more complex information to prove that the debt really truly is yours and they really truly have the authority to ask you to pay them for it.
If you want the pucker factor to increase for the CRA in the mean time, you can always MOV the CRA. That way you'll have both ends of the problem looking into it for you.
-ivyalmighty