Grey out Z-axis/Blue-channel of normals in Material Shader

So I’ve been doing a surface tension map set up with my material and textures. A part of which I need to get a normal that I made and “get rid of the Z-axis”. I was able to do this easily in Photoshop by replacing the Blue channel with a solid 50% grey. I attempted the same in UE, by splitting the components, appending a 50% grey to the blue channel back to the RG values. The blue is 50% value but still retains the same 100% saturation. I’ve tried a number of attempts with the desaturation node, multiplying etc. with no luck.
I’m wondering if anyone has any ideas how this can be correctly done in UE or what’s causing this to happen compared to Photoshop? I attached a screenshot below