I've seen many mention this but I don't really follow.

So 10psi through the intake cycle is also filling the cylinder, so there will be a pressure differential across the valve but not by the entire 10psi.

As the piston is coming up and intake valve is closing, there is pressure in the cylinder and as soon as the intake valve touches the seat you begin compression cycle and cylinder pressure instantly far exceeds manifold pressure.

Just not understanding the theory behind that I suppose. (boost subtracting seat pressure). I'm no expert on diesels but from what I've read it doesn't seem like they use much valve spring but some with compound turbos are at 150+psi boost.

More of a problem on the exhaust side of a turbo motor IMO (valve trying to close against turbine drive pressure as intake valve is opening)