Mutt,
The logic you may never find.
The rationale, as I accept it, is that the VMCG is determined at the performance testing stage to meet FAR25 requirements with Nosewheel steering made inoperative in zero (or up to 7 Kt) Xwind and an engine failed.
The crosswind capability is determined at a different (handling qualities) phase of testing with Nosewheel steering operative, also with an engine failed, different FAR (not one that I use regularly, don't have the number, sorry).
Just take a look at the Xwind limit plummet towards zero when Nosewheel Steering Inop is considered from the 'handling qualities' perspective in other 'Non-Normal Procedures'.
The very significant determinant, VMCG, is evaluated with Nosewheel Steering Inop AND an engine failure, but the on-going assumption for day to day operations (at least at the Takeoff phase) does not consider multiple failures, in this case both an engine AND Nosewheel steering, thus allowing normal steering capability to be factored into Xwind limit evaluation.
Good to see you're back from the Emerald Isle Mutt, it was becoming quite boring without you.