Thanks Peer,

Your CAD forensics are impressive - all makes sense I was wondering were PIPEBEND was collecting the bend info.
I did think there was an underlying structure difference between Parasolid and Open Nurbs and the way the surface was created.

I tried a part from SW without Tangent lock and same curve from Moi and that imported AOK into pipebend so yes that curve pathway is tangent - but have a look at the MOI Fillets file that was a series of polylines with fillets applied and then shelled. That solid imports into PIPEBEND aok so strange it structures the surfaces in some instances in same fashion and then in other style that PIPEBEND cant read.

Really appreciate the insights.