There are two major issues with harvesting ("shucking") external drives:
In many 2.5" external drives, the USB connector is soldered onto the drive in place of the SATA port, preventing any other use case.
External drives are the lowest bin. Hard drives, like processors, are binned based on their expected performance and reliability. The best drives go in datacenters (e.g. Ultrastar); good drives are marketed towards specific consumers (e.g. WD Black for performance-oriented storage, WD Green for cheaper storage with shakier reliability, WD Red for quiet, reliable NAS systems), and external drives are basically the HDD equivalent of what goes into a sausage. These are the drives that come with a laughably short warranty and fail not long afterwards, since they're too bad to be used even in the lowest bin of internal drives. I have had problems with almost every single 2.5" external HDD I've gotten my hands on.