You're correct- beehive springs have amassed a record of occasional breakage both in competition and on the street, and since they are always run as single springs, spring breakage is almost always instantly followed by that now loose valve following the piston down into the cylinder. Massive damage usually follows as the piston travels up with the valve now inside the cylinder, including split cylinder walls and destroyed heads. Aluminum heads and blocks can be repaired easily but not cheaply. Serialized iron blocks with a damaged cylinder can be sleeved but a punctured iron head is a total loss.
FWIW: conical springs such as those sold by Comp Cams have the same small tops and lightweight retainers like beehives do, but are straight-wall-shaped such that a second conical inner spring can be fitted for 'insurance'. Beehive springs have a curved profile; so far, no one has made an internal 'insurance' spring to fit. Unlike straight dual springs with dampers, the inner and outer springs of conicals do not contact each other or use a damper so friction and oil heating stays low.
The performance parameters seem to be identical for beehive and conical springs (light weight, small retainers, low oil heating and rev-range extension). When I upgrade my own engine, I will likely use dual conical springs but NOT Ti retainers; tool steel retainers are stronger, do not abrade like Ti and are within grams in weight.