Instructables are crap, never try and learn stuff from them.
A common beginners mistake it to think two Arduinos are needed for a project in 99% of the time they are not, it is just that they don’t know how to program or how to add extra pins to the board they have.
The Edison is a 3V3 system, with very slow I/O, all channeled through an I2C expander running at 100KHz, and the analogue inputs have a sampling rate less than 1KHz and a socking big capacitor on the inputs. Not the best designed board in the world, but Intel designed it and had it in mass production in 60 days.