Obviously I like 'em and have never had any issues with fret wear.
because there is NO issue. this legend has it's roots back in the days when the only company making roundwound strings was Rotosound, and being them steel&round against the most common flatwounds, they obviously ate frets.
we know that legends like this are harder to die than John McClane, and even now that there are rougher strings on the market, Swing66 are still considered fret-eaters...
I've used for many years the Swing66 on the same bass, and never had a big fretwear, nothing more than the other basses with nickels or other stainless...
it's just a legend, or in case it's just a matter of scum-alloy used for frets.