So I decided to have a look at taking external hard drives apart. Something the data storage community (e.g. /r/datahoarders) call "shucking". You buy external drives, open them up like a clam, and take out the meaty goodness.
For various reasons hard drive manufacturers have wildly different pricing and channels designed for intended "use cases". In general much of this is cosmetic and if you aren't paying attention you can spend 2-5x the price of a plain old hard drive for no good reason.
Therefore I bought two USB powered external miniature drives and opened them up. One by Seagate and the other by Western Digital. Both claimed to be USB 3.0 drives with 5TB of capacity. However they were two very different kinds of drives.
First off, the connection to the computer came up as usb-storage for one and uas for the other. For those that don't know, the simple difference is "uas" is better than "usb-storage". The former allows for advanced SATA features such as command queueing and letting the drive optimize access. The latter is a bit dumber.
Western Digital (usb-storage) 5TB $99/Amazon
The western digital was fairly easy to pry apart, though not without marring the case. Inside we see what at first looks like an ordinary hard drive.
Seagate (uas) 5TB $109.99/Amazon
The Seagate on the other hand reveals a nice surprise.
That's a nice little accessory card that incorporates a USB3.0 to SATA connector. It's like getting two toys for the price of one.