This is correct. Using meta tables in this way makes function (and variables if you want) definitions effectively static saving on memory (although look up will take slightly longer).
Please note that this tutorial isn’t designed to be the definitive best way of doing oop in Lua. Honestly the best way is whatever let’s you code best and most easily. This tutorial was meant to demonstrate oop without external dependencies and minimal boilerplate code whilst retaining features such as inheritance, operator overloads and (somewhat limited) polymorphism, with minimal impact on performance.