It is true, biometrics provided for super/visitor visa are valid for 10 years only for another super/visitor visa.
For PR applications, a new biometrics is required.
I don’t know the reason behind it, but that is what cic’s website says.
Exceptions are given to some people whose parents were present in Canada at the application submission time, but those exceptions were even given to people who never did bio in the past.
I know it is strange as biometrics are the same and should not be requested again for PR application but that is how it is.