Because you cannot use a HKSAR passport to enter China. I assume you do not have the HRP, so that's a good enough reason to "be Canadian". If they want "proof" of your Chinese name, the HKID would suffice. Under current policy, nothing bad will happen "if they find out". They're just not interested. Everyone of them should understand that for a HK ID-bearing Chinese national, acquiring foreign nationality does not mean automatically losing Chinese nationality, which is the case for Mainlanders.