So if they defer (or don’t defer), and thus get the match as pw (or they get no match), that deferral election can also affects their wages that are required to be paid, not just their match. So the match and the wages can both be contingent upon the election to defer.
For example, a pw contract requires $42 per hour. The plan does a pw match equal to a dollar for dollar match of 5% of pay.
Gilligan’s pay is normally $40 per hour. He chooses to defer nothing. That election gets him $2 more per hour in wages. Next time, Gilligan elects to defer $2, and that election gets him $2 of match but no extra wages. Finally, on the next job Gilligan defers $1 per hour. This deferral election turns into both $1 of match and $1 of extra pay.
IRC 401(k)(4)(A): Benefits (other than matching contributions) must not be contingent on election to defer.
The amount of extra wages required to satisfy the contract, are contingent upon deferrals. Does that violate 401(k)(4)? It’s not a problem with the pw contract, certainly any type of employer contribution can be used to satisfy that. To me it’s a tax qualification question. IMO, the most solid ground here would be to have a document that has IRS approval for using prevailing wage as a match. Maybe that’s too cautious?