Ah, that makes sense. I thought the $197 was for a Samsung SSD, not a mechanical drive. That is a bit steep.
My inclination is to say that Sound Devices are being cautious in their advice. I'm sure they invest a lot in testing various media and take reported issue seriously (as evidenced by their recent post-release removal of compatible CF and SD cards for the 664 mixer) and of course SSDs are all over the place in terms of controller chips and firmware. Even if they tested and recommend a specific SSD brand and model for use with their older generation recorders, it probably won't be available for more than 6 months and they'd have to stock outdated SSDs as parts. Speculating here, of course.
If $117 isn't going to break the bank and you've got a few SSDs laying around for testing, I'd say go for the adapter. It'll probably work and I'm sure a few others can and will confirm kingkita's experience. Glad to know this is an issue with 744ts since I would want to do the same.