I am not sure of the reason for the rotation of the valve in your video. It may have some type of bearing to allow rotation, or the springs may be out of control due to age or RPM.
A valve will turn a tiny bit each time the valve opens due to the twist imparted by the compressing of the spring. If there is sufficient friction [ie no rotator provisions] then the valve will turn back to it's original position as the spring returns to the seated position.
A valve that rotates all the time requires either a collet designed as a bearing -ie with the ends of the collet butted together or a rotator bearing cap or seat.
Most valves will rotate at some rpm, where there is enough separation from surge to reduce the friction between the spring and cap or spring and seat. This allows rotation without serious spring wear -although it usually signals the beginning of the loss of valve train control.
Rotating valves was once common on gas engines using leaded fuel. It was needed to scrub the lead buildup from the valve and seat.
If the lead is not scrubbed, the valve is insulated from the seat and without heat transfer,
the valve will overheat and burn.
The problem with rotating valves on an unleaded fuel engine is the buildup of hard deposits on the valve that is a byproduct of burning gasoline. These hard deposits on the valve make the valve into something akin to a grinding stone. If the valve lands on the seat while it is rotating, then more wear occurs.
If the valves are rotating at common cruise RPM, then you will have wear problems unless there are designed in precautions. [ special hard parts]
There are a few [rare] engines still rotating the valves with unleaded gasoline. They use very hard, high temp materials for the valve and seat -usually inconel.
Rotating valves are still used on diesel engines to scrub soot from the seat.
Burning diesel does not produce these hard deposits on the valve, so wear is not an issue.
