As Dirk mention, Philippe may be a disciple of Bourbaki and is attempting
to bring more formalized rigor and abstraction to Lua.
-spc (Or maybe not ... I do not with to contradict the Great Philippe
Verdy with false inferences)
You made a false inference, because I don't know and don't have any contact I can remember of with this "Bourbaki".
Anyway formalism in programming languages is extremely useful, it allows finding design bugs and ambiguities, it allows to make the programming language better, more predictable, more portable, and more secure.
Even if this was not an initial goal, the success of Lua will cause the language to be scrupulously analyzed to find and solve its weaknesses or inconsistencies. Lua is not finished at its 5.3 version (or the new alpha version 5.4 currently tested...).
We can expect a major version 6.0 coming next (that will need to break some compatibility with earlier implementations outside the limits that will be documented and that are still not documented at all, or just implied informally by some existing known implementations), and certainly other versions to fix newly discovered inconsistencies or portability problems.
All programmers need precise definitions of the semantics and limits of their favorite programming language, in order to know before trying to use it, if it will solve their problem, or if their own development will fail and will be finally abandonned, or will need to be significantly rewritten from nearly zero taking into account the unsuspected limits with workarounds or some complex additional library/layer.