Most of the times I see crossed cables, it's where the fulcums are on the head tube below the line of the downtube, so the wires can cross in space, rather than wrapping themselves along the tube.

With the fulcrums on the sides of the tubes as described, I wouldn't cross the cables because it unnecessarily add friction. Without seeing the specifics I won't fault the mechanic, since things like this are often a matter of balancing pluses and minuses of the options.

Don't worry about the cables wearing where they cross because you won't live that long, and the cables will fail as they do at the head long before they wear at the cross. As for the frame wear, take a look and see how large the contact/friction area is, and if it's just a short spot under the tube, put a piece of teflon tape there.

OTOH, if the cables are actually rubbing on a large area of the tube as they wrap around it, I'd uncross them, both for cosmetic reasons and to reduce friction.