It's not a silly argument at all. There are many examples of clubs, for example, dropping players as revenge for signing contracts elsewhere, which don't meet the 'develop their replacement' standards of credibility in argument. Such as Justin Hodges leaving Brisbane to join Easts, Canterbury dropping Dean Pay to Moorebank for joining the ARL, and then sacking Jarred McCracken - clearly the clubs best centre at the time.
Then there's the old "sell the contract" trick, where a player with a year to run finds his contract sold to another club, and to honour his end of the contract, has to move.