I won't name any names either (to avoid any association whatsoever with your NDA), but there was a manufacturer a while ago (years ago, things could have (and likely have) changed) that was sticking multiple different internal drive models inside the same model of external enclosure. I, along with many others, began to assume that these drives were determined to be of lesser quality for some reason or another (vibration?), and thus stuck in externals with a lesser warranty.
I wouldn't expect any specific model of drive to be inside an external drive. I don't think this is because of any unscrupulous motive by the manufacturer, just "the way things are". Internal drives are sold as a specific model and some customers have expectations* that that is what they will get (while others won't care). External drives are sold as a given capacity / feature set and as long as that is met, the drive is suitable for its intended purpose. [I think we can all agree that people who shuck drives are using the drives for a purpose the manufacturer didn't intend.]
Using a variety of drive models, all of which meet the specs for the external drive product, is a useful way for a manufacturer to deal with a situation where production planning and reality don't align - for example, if a drive manufacturer is making a production run of drives for an OEM and that OEM goes out of business, the drive manufacturer has a load of drives that may or may not match any existing retail model. Putting them in external enclosures is a good way to sell them.
That may be where the idea about "binned" or lower-quality drives comes from - if an OEM drive (which normally has a less-than-retail warranty) gets put in an external enclosure by the manufacturer, then there would be a difference in the warranty. But the manufacturer provides a consistent warranty for the external drive, so there isn't really a difference (again, for the external drive's intended use).
Manufacturers then started making some drives specifically for external enclosures - there were some drives where the drive logic board had only a USB interface - no SATA, etc. Again, if the drive meets the specs for the external enclosure, the manufacturer has no obligation to provide a drive with a SATA interface.
There are many explanations for the price difference between internal and external retail drives. One manufacturer told me that their breakdown of sales (from smallest to largest) is:
- Boxed retail internal drives
- External drives
- Branded internal drives (bulk, etc.)
- OEM internal drives
Sometimes branded internal drives and external drives swap positions on that list. So the price difference may simply be due to volume.
* Model numbers can be a bit funny. One manufacturer divides the model number into 2 parts - one which shows the basic model of drive and a second which indicates the specific OEM the drive was made for, as well as variant options or running production changes. For example, the number of platters in a drive and the type of spindle bearing used would change, but the base model number would remain the same.
