Wire that is not a part of a UL approved NEC wiring method is required to be marked with certain information every so many feet. Since wire used in AC cable is typically not marked and only the tag on the AC cable tells you what type and size wire it is, technically I think it may be noncompliant.
Practically I think it is probably ok.
AC cable is not a raceway by the way.
No the short radius elbow cannot be buried.
