It might leave a sour taste but I think it's actually strategically a pretty savvy move.
It gives weight to idea that the Tories plan to deal with the boats is nonsense/not workable and at the same time it is evidence that someone who is invested in solving the problem believes labour has a better plan. One of the few things that has cut through recently is that labour are just blocking and have no plan, this combats that to a certain extent.