The Sachs image is from 1t least 1993, as it's done in Brilliance, which was released then. It's also in 256 colors, versus Treister's images from 1995 done when the maximum number of colors was 32. Unless you had a paint program capable of Hold And Modify mode, which DPaint was not at the time. (And Extra Half-Brite did not exist until the A2000 and A500 came out in 1987.)
And here's an image from Avril Harrison in 1985, which might have been one of the demo images that shipped with DPaint - I know several of her works were on the disc: http://amiga.lychesis.net/year/1985/AH_Waif.html
So let's have a more equal comparison: here's an image from Defender of the Crown (1986). http://amiga.lychesis.net/artist/JimSachs/DefenderOfTheCrown...
And here's an image from Avril Harrison in 1985, which might have been one of the demo images that shipped with DPaint - I know several of her works were on the disc: http://amiga.lychesis.net/year/1985/AH_Waif.html
And of course how about Harrison's 1985 image of Tutankhamun's death mask, which was both on the disc and on the cover of the box? http://amiga.lychesis.net/year/1985/AH_KingTut.html