Tbh it’s more like an edge-lit acrylic effect. We did call it a “subsurface effect” when I worked at Forza but may have been using the term loosely. Forza also was going for acrylic rather than glass and we had several acrylic samples around the office to play with.

That being said my example is not acrylic… and it’s not quite glass either as you mention. It’s more like glass with some artistic license.

I agree that it looks nice and similar to what SSS eventually renders like. But strictly speaking it's not SSS. Actual SSS happens when the medium is somewhat transparent (light can enter the material) but also diffusive (light gets randomly bounced around within the material). Glass lacks this second property. A good example of a material exhibiting strong SSS would be wax.

Not that this matters much anyway, the effect is cool nonetheless, albeit a little bit improperly named.