for the non-pedologists:
Sandy clay is a textural box on the soil triangle. It’s small and requires the absence of silt. The reason we joke about them not existing is because of the size of the box and how far apart the two grain sizes are. There are very few scenarios where sand and clay would be deposited and not silt.
So it is possible under some circumstances? I’ve actually wondered about this.
I guess it’s probably been created by people occasionally. I’ve had customers say they’re going to add sand when I tell them they have heavy clay. My colleagues always told me this won’t help but I’ve never investigated further.
The only references I can find for such soils are when there are highly stratified C horizons where a component may be sandy clays, like the Lohmiller series, at least that’s my interpretation of the description
https://soilseries.sc.egov.usda.gov/OSD_Docs/L/LOHMILLER.html