I am using 4.0. In my test I used total transmission and roughness 0. This is “similar” to glass, although the glass shader still looks better for me.
In your example you are adjusting the IOR of the reflections only, (there is no transmission/ refraction), your base colour is black, if you adjust the IOR in this case it just makes the reflections get lighter and darker in a similar fashion as adjusting the specular value in the old principled shader. This does have a sort of “fresnel” effect too.