That’s nonsense. No one can afford to require licensed people (which they need to hire today) to spend years on deck before moving up.
Working on deck is no longer the route to the wheelhouse.
Today, going to an Academy is the primary route to a tugboat wheelhouse.
Many companies will hire any warm body with a license for a Mate of Towing position.
Crowley for example.
Centerline recently advertised that they were looking to hire and train licensed Mates with no towing experience and no towing endorsement.
Fishermen with Mate of Uninspected Towing Vessels 3000 tons typically make the transition to Mate of Towing as soon as they get their new towing endorsement.
If some tugboat company is telling you that they want you to spend years on deck before moving up to Mate, that’s not the real reason that they are not hiring you.
They think that there is something else wrong with you. Maybe you are too old, too fat, you act like a pain-in-the-ass, you put your pronouns on your resume, or whatever. The real reason they are telling you that you will have to work on deck for years is that they simply do not want to hire you.
If you have Mate of Towing, and you are otherwise a desirable employee, you will be on the fast track to the wheelhouse.