I'm just trying to imagine with physics... Any time the valve is open, the pressure on either side of the valve will be very close to equal. With the pressure close to equal on either side of the valve, the valve will close if the cam is not pushing it open and it will stay closed until either the cam pushes it open OR there is significantly more pressure on the back of the valve than there is on the front.
Thinking about intake valves if the intake pressure is very high... On the intake stroke, the pressure in the cylinder will be lower, but the valve IS open by the cam. Near the start of the compression stroke, the pressure inside the cylinder will be the same as the pressure in the intake manifold or darn close. Because the pressure is normal, the cam and valve spring will close the valve. The pressure in the cylinder will then rise abruptly and vastly overtake the intake pressure so there is no chance of the intake valve opening during the compression stroke or the power stroke. On the exhaust stroke, the cylinder pressure will be higher than the exhaust manifold pressure and definitely higher than the intake manifold pressure so no chance of the intake valve opening during the exhaust stroke. Ok... intake valves cannot be blown open.
Thinking about the exhaust valves when the exhaust manifold pressure is high. During the power stroke, obviously cylinder pressure is much higher than EMP - exhaust valves will not be able to open. On the exhaust stroke, the cylinder pressure will normalize with the exhaust manifold pressure - exhaust valve is open by design. On the intake stroke, if the exhaust manifold pressure is higher than the intake pressure by enough of a difference to overcome the exhaust valve springs, some exhaust will leak into the cylinders. On the compression stroke, the cylinder pressure will quickly overtake the exhaust manifold pressure and keep the exhaust closed through to the end of the power stroke when it opens by design.
My conclusion... intake valves cannot be 'blown open', exhaust valves could possibly be blown open on the intake stroke if the difference between intake and exhaust manifold pressures is very high, and there is not any situation of valves being blown open that can result in piston/valve contact.
This is just my attempt at a logical assessment based on physics and it could certainly be wrong due to my missing some key factor. At this point, though, I think it's solid thinking.