I’m sorry but I still don’t get it either. If it’s hot enough, you’ll know it’s ready when it starts melting whatever you use to solder. Why would one need anything more?
As a general rule, anything that uses electricity to get hot is going to need to run a PID if you want it to maintain a stable temperature. Once you've got the microcontroller in there it's trivial to add nice little features like thermal runaway detection or auto cooling/auto heating when the iron is put down/picked up, which are a couple of things the pinecil does.