This is most intriguing: I have two HDs, both recovered from Windoze laptops. Both mount OK on the MBA. With both drives, when I connect via the Seagate GoFlex Thunderbolt/SATA adaptor, TechTool Pro announces both are failing their S.M.A.R.T. STATUS. In these cases, TTP shows the drives in its test application window.
Yet when both allegedly dodgy drives are connected via a Seagate GoFlex USB 3.0 adaptor, TTP doesn't show them in the test app window & the TTP monitor app doesn't detect anything wrong with them.
I'm about to try via a different connection, this time a Kanex Thunderbolt-to-USB 3.0 adaptor.