An event (If statment) causes all statements in the piston to be evaluated when the event occurs.
Switch 1 and Dimmer 4 both toggle whenever Dimmer 6 changes.
I’ve just discovered that a timer (Every statement) in a piston only causes that statement in the piston to execute when the timer goes off.
Switch 1 is toggled every minute. Dimmer 4 never changes.
This is a bit of a surprise to me. I hope the information is helpful to others.