To be fair, these types of necessarily clientside restrictions as "rules" exist in many popular games: Starcraft 1 and Warcraft 3 for example had a limit on the number of units you could select / command at once: there is absolutely no technological way for the server to enforce such a restriction if clients can be modified, but its a deliberate game rules restriction.
It sounds like your understanding is "the game is the server sends and receives packets: the goal is for the server to say that you win" which would be a view mischaracterizes almost all player's expectations: if you just wrote a client that has AI playing that only uses the info a player has that would also be very clearly cheating even if it only acts on information that players could act on.
It sounds like your understanding is "the game is the server sends and receives packets: the goal is for the server to say that you win" which would be a view mischaracterizes almost all player's expectations: if you just wrote a client that has AI playing that only uses the info a player has that would also be very clearly cheating even if it only acts on information that players could act on.