Not smoke & mirrors in my experience. In fact, you should be able to feel the difference, just by running your fingertips over the surface of them. So try that sometime, comparing the stainless steel Lo-Riders against any well-known conventional stainless steel roundwound string, such as ProSteels, Dean Markley Blue Steels, or Rotosound Swing Bass 66s. That relative roughness and rawness of the outer wrap on the roundwounds translates directly into more roughness and rawness in the tone of the strings, relative to the DRs.
I honestly was on the verge of swearing off stainless steel strings permanently - before I decided to give the Lo-Riders a chance. They're not a crunchy rock type of string, that's for sure. But they're not a typical harsh, "clanky in the upper midrange" type of stainless steel string either. Consider me a convert.
I use FatBeams on my fretless basses, love the smoothness and low-midrange focus of the tone, and have never noticed any particular "scoop" in the midrange. Different sets of ears hear different things, I suppose. And one's gear, settings, playing style, preferred genre(s) of music and general tonal preferences all play a role as well. But I've never noticed anything missing from the FatBeams...
MM