I don't find the knot solution to be at all problematic. Maybe in another universe or given infinite time!
True that some types of rope are prone to untying themselves with a bit of jostling, but not the material of which the Leica strap is made. When I cut the excess, I use a heated cutter so as to fuse the end to prevent fraying, and I apply Dritz Fray Check or similar to the knot. I use the same technique in many other applications and haven't yet had a knot fail (in 30 or so years, using this method with scores of knots in long-term applications). I prefer the figure-eight knot for this application, by the way. It's a good stopper knot, would easy to see if it were coming loose, and is possible to untie if one wishes to remove the strap.
Also true that (some types of) knots can dramatically reduce rope strength, but given that the Leica strap material can supports at least a hundred kilograms, I don't think this is a concern given that the bins are only a fraction of a kg in mass. Maybe, instead, we should be using breakaway clasps (like on cat collars) as a safety measure!
--AP