In Disk Utility, both drives are shown as a single logical group. So, Apple would have to show each drive separately in order to read the S.M.A.R.T. attributes in the current Disk Utility. They likely won't do that, because it would confuse some users. Since this logical volume technology is new to Apple consumer products, give them some time. The will probably make the "Verified" or "Failed" status available in a future update of Disk Utility.
Onyx is likely the same way.
If you wish to read the S.M.A.R.T. status, you should be able to boot into an external drive or to the repair partition to see it separately on both drives.