Minecraft wiki entry for Egg_farming, associated text: Frilioth puts the dispenser at the slab (chicken) level in the meat farm. This allows fewer layers of construction to be used and makes the design much simpler.
Another innovation is that the system is self-powering: by letting a comparator analyze the first (egg-carrying) hopper and an observer amplifying the signal, the egg-shooting dispenser can automatically fire (twice) without a clock circuit constantly working.
Instead of being constantly there, the lava is controlled by another dispenser to only appear for two ticks. There is no real benefit to this level of caution, before 1.14 at least.
Since 1.14 the lava destroys the cooked-chicken drops almost instantly. Frilioth has published a guide to upgrade the farm. The idea is to replace the hopper with a Minecart with Hopper sitting directly on a hopper while keeping the same slab mechanism. The minecart collects items much faster so all products can be saved from the flame.