I thought I was crazy but BC250 on stock cooler indeed only work with a certain orientation.
I used to run my board without a case before I bought my mATX case and the orientation was vertically 180⁰ off which means the I/O shield is on the right side with the heatsink facing side panel (PCIE facing up)
After I got my hands on the mATX case, as how the case was traditionally designed, I need to rotate the board 180⁰ so that the I/O shield facing the left side (PCIE facing down)
My temp suddenly goes up to 10⁰C more, on the same game, on the same settings. I thought it is because of the mesh panel, but after removing all the panel the temp remain the same. I did everything I can and the only way I can reduce the temp is by turning down the resolution and in game settings.
Then I stumble upon a comment from one of the member here saying that the heatpipe was designed with a certain orientation or else the fluid inside the heatpipe will be fighting the gravity. Then I did a research and indeed some heatpipe are designed to work only with a specific orientation or else the system will experience a jump of up to 10⁰C in temp.
As you can see, I did some testing with the board laying flat and I got my old temp back. I think we need more testing to verify this phenomenon