I think the idea is if the liver is not releasing copper, then liver copper levels can be high, at toxic levels, but serum copper levels can be low.
Supplementing it constantly may immediately improve serum levels ( by bypassing the liver blockage), but then you have extra copper burden on the liver, and further decrease in function.
For this reason excesses -> blockage-> deficiency.
That is the theory anyway supported if people eat a low copper diet, improve their liver function, and see serum copper increase despite eating less copper.