You still lose thermal conductivity and manufacturers should not make a trend out of it. Unless the CPU and GPU rad are used in a server room with high humidity where those rads need environmental protection against oxidation and corrosion, plating, anodizing or painting should not be the norm for general use.
Humor me and ask Kingpin why he didn't plated or anodized the radiator fins or the cold plate on his designs, why bare copper? Same with the water blocks. Doesn't liquids can bring corrosion more than humid air? Yes, but you create a coolant that prevents that.
Some Copper alloy will oxidize faster than others, they just have to use the right one and not cut costs all the time.
Now days around 80% of all cold plates are plated with NiZn but, how many users will lap or at least scratch the cold plates to see how much Copper is there if any or is just Aluminum.
On the other hand end users bite out hard in the color schemes created by hardware manufacturers, in the first place, and now in some cases is the end user asking for colored radiators.
See: Be Quiet Pure Rock 2 which was bare metal at the start, user start to ask for black and white rads the Pure Rock 2 FX which got heat pipe modifications for more RAM clearance, comes only painted(
electrophoresis coating) while only old Pure Rock 2 comes bare metal.
Just a glance why cold plate shouldn't be plated.
NiZn alloy 21 to 33 W/m. K
Ni 60.7 -90 W/m-K
Copper alloys 400 w/m-K
Aluminum ~230 w/m-k
When you choose CPU cooler you have to see the clearance from GPU backplate.
If are too hot CPU will throttle down, GPU will throttle down, VRAM will fry and you have to rely now on integrated GPU till you replace/repair your main GPU - is worth it?
When I built last system I went for Pure Rock 2 instead of Pure Rock FX, just in case I need the clearance for a fan. Also PR2 is bare metal while FX is coated. PR2 will be enough as can go up to 150W and CPU will go max to 90W.
Are you willing to change you CPU cooler for 10C less on your GPU? maybe more or maybe less than 10C, I would but that's me.
On the other hand are slimmer fans 10 mm or 15 mm(which might fit in your setup), less effective but, better than nothing.
Back in time I had this GPU with a bad designed cooler, I found my self another cooler.... and than I emailed Power Color not being confident of Zerotherm cooler will fit on their X1950XT card knowing ZeroTherm was new on the market.
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In plenty cases users showed to be more interested and had better ideas in finding solutions, design or improve existing designs than the manufacturer who is blinded by profit margins or can't care less.
Do what you will with this. I have no interest to show you wrong data on cooling solutions but, a manufacturer will have interest to tell you their cooling is enough, isn't it?