I don't necessarily disagree there. But training a SF needs time, no matter what kind of SF you want. If anything, you should tell people not to train SFs if they aren't experienced managers and do need to have success soon. Which is more or less what you told them, yes; but the advice shouldn't be to train badly skilled SGs but to train Guards as is. You can still use a Guard as a SF some time - just don't expect him to be reliable defensively or flexible offensively.