this is CPU to GPU:https://www.amazon.com/Female-Adapter-Splitter-Graphics-COMeap/dp/B07CZCFFST
this is GPU to GPU:
https://www.aliexpress.com/i/32848383734.html
As you can see, they are similar. Vendor could send you wrong splitters. Look closely on splitter that you got.
Easiest way to distinguish them is by looking at wires. cpu to gpu has only black in 1 row and only yellow in other. pcie to pcie has only black in one row and second row has 3 slots with yellow wires and 1 slot with black wires.