No, at least one other person wondered about it and still does.

Here's some possibilities I've come up with.

The nature of round vs. flat contact is such that the contact area is tinier, so a notch is worn in quickly preventing relative movement.

Depending on the hub and how spokes are attached, flat spoke wheels may not have as much deflection caused by interlacing, and so not as much force pressing them together, therefore lower fiction at the cross to resist movement.

Flat spokes may not be perfectly in plane where they cross, so torsion may be a factor.

There are probably other considerations, but since I've never heard of this problem on the few bladed spoke wheels I've built, I've never thought about it until this thread. I suspect the second possibility may be likeliest.