I mean it's tongue-in-cheek, and it's never really been a problem at my table. Just a fun way to remind casters not to argue about specific wording interpretations in spells, and take them as their most obvious meaning
Now, if a caster comes up with something clever, they can make an Intelligence (Persuasion) check to see if Mystra will allow something. Just don't tell Mystra how her own body works