PSA Check your expansion tank overfill hose

So I installed a brand new correct 16 psi radiator cap, after a drive to test it I noticed a bit of coolant splash on top of the expansion tank, so I waited for the car to cool down and when I tried to pull the cap off it was harder than usual (a vacuum was created)
I checked the hoses and everything looked fine, then I blew into the overfill hose and nothing.
I removed it and the part where you connect the hose to the tank was completely clogged with black oxidized material (rust maybe?), I needed to use a nail and a rubber hammer to open it up, once open I used a skewer stick (along with the rubber hammer) to push the rest.
Tip: you need to hit from outside (due to the angle) so I found that a coca cola cap blocks the opening perfectly to prevent that you push parts of the clog inside the expansion tank.
I think this is pretty often overlooked and could create problems like coolant splashes or a vacuum.
I wonder how many people have clogs without knowing.
My car was running perfectly, not overheating nor anything but I had an incorrect 20psi cap so my guess is that the cooling system was already leveled at such pressure so I didn’t notice any splashes before, but the 16psi cap puts less pressure therefore was a bit of a splash due to the leveling process (And also I had a bit of extra coolant in it 5cms to the neck vs 6cms)

Hope this helps