It should be simple, the Devs say it is, therefore it is.
However, sometimes, the devs have to figure things out and check stuff, are not aware, or aren't really very interested because they are interested in more exciting things.
For instance, the now infamous grade 5 mods, using grade 1 materials.
Clear cut, but, Frontier didn't explicitly state it was an exploit until a good while after it existed.
Less clear cut things are when frontier has it's own ideas of in game progession, and they don't realise there are methods to circumvent their design (unintended) to bypass the intented behaviour, however, no bugs are used.
Such as when players find a particularly lucrative method of gaining credits/rep/rank/BGS influence, which frontier were unaware was possible, AND which may take considerable development time to fully "solve"
Frontier might leave it around unless it's completely nuts (missions directly granting quadrillions in one go) but it's not the design they intended.