Technically they printed it for a mold but that's because fiberglass is better and while you can can print with glass reinforced materials the fibers have to be quite short which reduces their tensile strength compared to composite sheets.
That said if you really wanted too you could print a functional hull, but it's not a good application for it.
Not every manufacturing method is appropriate we can CNC mill a car from a single block of aluminum too but it's not exactly a good manufacturing process for this task.
EDIT: HanseYachts AG apparently prints a 10m (~33ft) hull for one of their Yachts using a cellulose composite filament.
You could do that, but it wouldn't be a good idea. Fiberglass works very well for that application and is much cheaper, faster, and higher performance.
It seems very large portion of yacht cost is interior installation. Printing might lead to all sort of safety, maintenance, performance and comfort advantages that you can’t achieve with normal manual labour.
I’m guessing some sort of hybrid approach could win.
What would it take to print 45ft yacht hull?
And not just the mould, but the hull itself?