Fords concern with BD/Dino over 5% is based on the acctepted ASTM standards for diesel.
There are no standards for BD other than that to be used for blending.
Blends of 5% or less will still meet the standard for #2 Diesel while blends over 5% may not. Thus most diesel engine makers limit their recommendation to B5 or less so they can be sure of the quality of fuel being used.