The most recent documentation to the ABQ_PLY_FABRIC VUMAT I found, mentions that transverse shear stiffness for shell elements must be specified: 
"When user-defined materials are employed to define the material response of shell elements, ABAQUS/Explicit cannot calculate a default value for the transverse shear stiffness of the element. Hence, you must manually define the element's transverse shear stiffness. See “Shell section behaviour,” Section 24.6.4 of the Version 6.8 ABAQUS Analysis User’s Manual, for guidelines on choosing this stiffness."

I'm using this material model for bending load cases, in Abaqus 2025, without specifying explicitly the transverse shear stiffness of the shell section. Hence, there must be a default value for the transverse shear stiffness.

Is there maybe any updated documentation (post 2009)?
Is it eventually calculated by the default procedure, or is it different? 
If it is different, how is it calculated then?