The drives in external units are the same as internal ones
I know that, I already disassembled some, even a CD drive to replace it with a DVD. But perhaps due to the interface that converts the firewire/USB to PATA has some issues and destroys the disk.

Also this Maxtor drive has no on/off button, only an on/off switch, meaning when the drive has finished its actions, you have to switch/power it off, which could be bad for the disk when it still writes/reads. Not parking properly or something like that.