But what is the “something different”?
— If you want to be rigorous then, yes, you DO check for a valid sequence (your arguments notwithstanding). This isn’t easy in Lua (see my other post).
— if the “something different” is “malfunction, not my problem” then that depends entirely on the nature of the malfunction. In our work the result of a malfunction can be “the patient dies”, and just pointing a finger of blame to another part of the system isn’t acceptable.
I’m fine with the Lua libraries not doing checking, but extending that to “no-one else should either” doesn’t seem a good argument to me.