Whoa. We have more than one issue involved here and I'll try my best to explain without adding to the confusion.
First, leaving aside the USB issue for the moment, you are running two different versions of the Reflect application. In that context, you need to be aware that Reflect v6.x can handle backups created by Reflect v5.x, but not vice versa
. In other words, the Reflect version that runs on the server would not be able to mount or restore a backup created by the Reflect version that runs on the Workstation. Nor would rescue media that was built using Reflect v5.x be able to do so. I'd highly recommend upgrading your server's Reflect installation to the current v6.2 version -- and your rescue media builds as well. Reflect v5 is no longer supported.
None of the foregoing has any bearing whatever on the issue of rescue media support for USB3-connected drives. That depends entirely on the inclusion of required drivers in the WinPE build regardless of which Reflect version is used. Rescue media builds based on PE 3.1, which is the recommended version for use with Windows 7 and earlier, do not provide "native" support for USB3 and therefore require the inclusion of the same added drivers needed for supporting USB3 in Windows itself. Later PE versions, on the other hand, do provide the same "native" USB3 support as the Windows versions from which they are derived and therefore do not require other drivers to be added for that purpose.
Hope that's clear. If it isn't, please don't hesitate to say so.
Regards, Richard V. ("Arvy")