Why does new Time Machine & Migrate fail with SD
A common Time Machine backup drive (with the root folder /Backups.backupdb/Computername/... only) itself is no bootable system. You always have to boot from Recovery Mode, Internet Recovery Mode or another bootable drive containing a bootable base or full OS X.

Booted to one of the mentioned systems allows you to restore the Time Machine backup to your main volume.

Additionally bootable systems require a GUID partition table and the volume has to be formatted with either HFS+ or HFS+ journaled. The latter is recommended/required for Time Machine backup drives. You may use an ExFAT volume but this needs additional configuration: you have to create a sparsebundle file, mount it and choose this one as backup volume.