You’re welcome, John. I forgot about the low light source elevation. Now fixed.
That’s with elevation 10°. Obviously without long cast shadows. I added elev=10 to the command. If you need the cast shadows then raytracing is the way to go.
lelandshade(G, detail=4.0, contrast=4.5, zfactor=5, cmap="t.cpt", azimuth=215, elev=10, show=true)
texture shade with detail=4.0, contrast=4.5 is pretty much a uniform grey image without any visible details. There is no point using such combination imho (or there’s a typo).
So… is this in regular GMT now? 
You’re totally right. Copied the wrong stuff. Try detail=0.045, contrast=6.0 for a better result.
As far as I know only in GMT.jl but maybe you can persuade @Joaquim to make it available in regular GMT 
Well I knew that was the wrong stuff.
Problem is that by “just” calling lelandshade from GMT.lj the user has no way of seeing that parameters of leland texture shading algo were not useful, because the result of texture shading was not shown to the user. By just calling lelandshade the user has no way of knowing whether e.g. lelandshade has been provided with nonsense combination of detail and contrast. These two must be selected manually depending on the plotted reilef.
The best way of tweaking this type of shading is to always plot the color map and texture shade on separate plots so texture shade can be checked visually. This is why my spaghetti code did 6 plots incl the final blend as shown above so the effect of these different parameters is shown and the result can be meaningfully tweaked. E.g. many color maps wouldn’t work well with this shading approach or might need tweaking (like the blue crater spots on the map above does not appear to me as the best way of representing these craters), Z scale exaggeration might need tweaking, % of texture shade in the final blend may need to be adjusted.
PS OK this was the best way I happened to found. If anybody knows better, comments are very welcome.