Hello samkooke,
Your observation is probably correct, although I cannot speak from personal experience. Not long ago, all openembedded based environments only produced a tar,gz file with SH4 images. Persian Prince of OpenvisionE2 has taken up the ardious task of adding/integrating both USB and flash components for SH4, largely based only my flash git. The status I have this is a work in progress at the moment, not helped by the fact that the last versions of fup (used to produce .ird files) all have problems for which I am largely responsible, and hope to fix this week.
Regards,
Audioniek.