[JJ_SO]

Who on Earth wants a 28-105/3.5-5.6 when a 24-105/4 or 24-120/4 is available in CaNikon's lineup?

  A Pentax K1 shooter who hasn't the wherewithal to reverse engineer Canon/Nikon lenses to mount on his K1?

You think, the Pentax K1 shooter really wants a 28-105 with variable aperture? Or, if he had a choice, would NOT prefer the 24-105 range? The Sigma 24-105 is rather mediocre wide open, but from f/5.6 it becomes really good. At least according to Roger Cigala: https://www.lensrentals.com/blog/2018/02/mtf-testing-for-the-sigma-24-105mm-f4-dg-os-hsm-art-series-lens/

The price of the Sigma is rather close to the admittedly nice price tag of the Pentax.