Section 409A applies only if it is a deferred compensation arrangement. A short-term deferral is defined as not being a deferred compensation arrangement. And the short-term deferral rule applies so long as the amount under a 457(f) arrangement is paid within 2½ months following the year of vesting. So a normal 457(f) arrangement in which amounts are paid on vesting isn't a deferred compensation arrangement, and can follow just the 457(f) rules, not the 409A rules.
The only time you have to worry about the 409A rules in the context of a 457(f) arrangement is if there is deferral beyond the year of vesting. I have seen this most commonly in situations in which the employer wants to provide an annuity payment. What you'd typically do in that situation is to provide that only an amount necessary to pay the 457(f) tax (which is the tax on the present value of the annuity) is paid in the year of vesting. Thereafter, the person receives the annuity payment each year. The annuity is taxable under section 72, meaning that most of each payment is nontaxable (the tax already having been paid in the year of vesting).
In that situation, you have a deferred compensation arrangement. So if, for example, you wanted to delay the start of the annuity payments, you'd have to follow the 409A rules. But if you're just talking about delaying vesting (and still paying out in the year the amount finally vests), you don't need to worry about the 409A rules.