I really wish the empeg fellas would consider opening up just the shuffle algorithm's source code to put this issue to rest.

OK, for the first time only, live on air, we're proud to present the entire of the shuffle algorithm source code! (For the non-custom-shuffle case, anyway.)

Here it is:

std::random_shuffle(running_order.begin() + from, running_order.begin() + to);

Good, isn't it?

Peter