MBTI is a theory that attempts to describe how the human brain functions: how it takes in information, processes and stores it, and how it spits it back out in an interactive format. Everyone has the same eight functions for doing all these things, but the order of priority each function receives is what gives us the sixteen different personality types.
But we clearly aren’t only sixteen people repeated over and over again, so there’s also a huge number of other factors going into our personalities – genetics, upbringing, economic status, education, gender, race and culture to name a few.
To use your example (ie, I have no idea if the ESTJ bread-thing is actually a thing), I would find it unlikely that every ESTJ would have the exact same favourite kind of bread, but it would be much more likely that ESTJs are the kind of people who would value having a favourite kind of bread.
