It appears that the defense was required to be on-premise to review the documents and was charged a fee by Imaging Universe to take copies with them. Requesting copies of all records shouldn't be necessary to obfuscate the defense's real documentation needs.

Come to think of it, shouldn't these records as a whole also be inadmissible because of the whole attorney client privilege thing?

Or is this just a "sneak and peak" tactic to get insights into the opposition's strategy?

No.

> Something about doctor-patient confidentiality?

Where it exists as a legal privilege at all, physician-patient privilege prevents certain information in medical records from being used against the patient in court. (And, in any case, it apparently doesn't exist in the Federal Rules of Evidence; there are federal laws on medical confidentiality, e.g., HIPAA, but they are not a general privilege against the use of medical records as evidence, and again they protect the patient, not the physician.)