The point of the criticism is to draw workers to you because what you say resonates with them. Sometimes it resonstes because they are already pissed. There absolutely were pissed UPS workers and seeing socialists say, "great job!" correctly teaches them that those socialists are full of shit. There are also workers that may not have been thinking of those criticisms but will be convinced by them. The key is to build constructive criticisms on top of congratulating the wins so that you don't alienate workers that are happy to have the contract. Trots tend to do that through their dogmatic and often hyperbolic criticism that is usually couched in esoteric language (either the workers aren't the intended audience or the Trot writing it is incompetent).
Re: Militancy, the UPS contract is denoted by a lack of it and closed door negotiations by staff who reached a TA far too early. The bar is set so low that Western socialists teach each other that just striking at all is militancy. It isn't. Militancy comes from strong worker organizer networks pushing demands, calling the shots on when to strike and when to agree, when to take other direct actions, and doing ds from a nascsntle class conscious perspective where they understand the boss as the enemy.