Reply To: Can a Fresnel node be plugged into Principled BSDF’s “Specular” slot to use an accurate IOR?

Good question! Not quite, because that would double the Fresnel effect applied to the shader and would also not result in an accurate value. Chris Plush explains the conversion between Fresnel and specular very well here: https://youtu.be/cvu5XYrZT6Q?t=199