I am a hardware engineer and former employee of a large computer company with that said i can give you a basic understanding that you can hack or reverse any efi password with the proper tools. all you have to do is reprogram the bios chip with a clean firmware that does not have a password on it. for this you will need a couple of things. first you have to identify the bios chip (microcontroller), then you have to get a .bin file that does not have a password on it and it has to be for your specific machine 2011 will not work on 2014 and so on.(that maybe hard to get since manufacturers own this info and do not give it out. thirdly you need the proper tools to do it. eprom programmer once the chip is removed from the board. this is just a basic description. I have seen it done and here is someone that can answer more in depth questions or do it for you. [http://jerseycityrepair.com/macbook-air-efi-password-removal/]
ok so here is a picture of the bios chip on the bottom right. It is the chip with 8 legs. it is the MXIC6406e CHIP and it is used in many computers not only macbooks but hp and many others. remember that most components are just that components and every company uses them. just the data onboard the chips are different.
thats the best I can do in a basic explanation. this work is on a engineering level that goes beyond the knowledge of technicians and is fully understood by those that can build a computer from its most basic components and make it work. In other words it not easy but it can be done with some education and skill.
efi password removal tool does not work don’t be fooled beware of those sellers because you will still have icloud pin and File vault locked hard drive.