Yes, agree.
What I do for deeper areas is use bonding or browning, but not everyone has that knocking about, then when that's gone off, I put Toupret on top.
When I started fitting these decorative metallic plates in the mid-80s, they came with a thin plastic gasket to separate the accessory from the wall, but most didn't get fitted. But if you didn't fit them, the guarantee wasn't valid and it was only a matter of time before the finish got tarnished.
Some manufacturers like Hamilton had an altogether better looking gasket that fitted the edges of the accessory and looked neater, but still many were omitted.
IDK if manufacturing processes have improved and there is no need for gaskets any more, but, once you have filled and sanded your Toupret, I would fit plastic sockets temporarily until the whole lot has had time to thoroughly dry out, then replace your chrome ones.