The shadergraph node "texelsize" does not return the correct value when you reduce the texture quality in quality settings. I discovered this while working with the surface gradient framework, where stepsize become mismatched once the texture resolution is reduced in project quality settings (Master texture limit). 

Documentation has this to say:
"The width and height of the texture object report the original, non-limited sizes. You may have to take this into account if you perform special sampling or processing with textures subject to the master limit quality setting, and you use masterTextureLimit > 1."

We have no way that i know of to access the master texture limit in shadergraph so it is hard for users to compensate (and somewhat obscure to discover that you need to do so)