I tried making a bowl farm using lightning rod mechanics.
I summoned lightning to the rod and it killed the turtles(adult and child) but they only dropped seagrass.
I then tested by summoning lightning without the rod on turtles and the same thing occurred(and I did the same for a full block and non-full blocks).
No bowls, only seagrass.

I only changed the gamerules doDaylightCycle and doWeatherCycle to false for this test world.