looking for “privacy issues” in iOS is like wondering if the sandwich you found in the sewer has healthy and organic salami, as if that’s the only issue preventing you from eating it.
you’re being spied on from the moment you activate it, including when it’s “off”, so does it matter if there are seven or actually nine things invading your privacy?
first off, if you plan to scan the storage for bad “sectors”, that’s gonna take eons if the disk is of any considerable size. what’s more likely is you running the SMART self-test and that will work over any medium.
the cables absolutely can and do cause corruption, whether it’s plain SATA-SATA cables or the USB-SATA with their own controller on it; however, if you don’t have reason to suspect this particular cable/adapter is faulty, it’s not a worry vector per se.