Utter bullshit. The computer serial# traces to the repair order at the shop. The contents of the emails have been authenticated (under signed statements). The meta data of the files can be checked for continuity, especially in the case of people who surrendered their matching emails to the Feebs and Guiliani. Same for the damning photos we've been seeing. That meta data can (but not necessarily) pinpoint the GPS coordinates, as well as the date/time of the pictures. Usually the model and possibly the serial number of the originating camera is included. Remember: Guiliani had the image of the drive and could access all of this. So does the FBI, as well as the actual computer. They may be slow-walking it, but they probably didn't actually destroy it.
There may even be a receipt somewhere indicating Hunter or his company (stop laughing) purchased the computer factory-fresh from a vendor like Best Buy or Dell.
They verify ballistics on bullets pulled out a murder victim with less.