While attempting to create a monostable circuit using snowballs thrown from a dispenser onto a wooden pressure plate, I saw that they did not activate it. Upon further testing, I discovered that not only do thrown snowballs not activate pressures plates, but that fire charges, lightning bolts, splash potions, and eggs also do not activate them. This being even though pressure plates can be activated by experience orbs, arrows, and even primed TNT.
P.S: This issue is most likely WAI because the projectiles in question are destroyed upon contact.
To reproduce, see the files below...
Exactly. Pressure plates need entities to activate them.
In some earlier versions pressure plates could be activated by particles, but that got removed