This might be one of the most positive news stories I've seen in a long while. If we can make this work here we can eventually find ways to make this work at scale.
In my opinion it's not absurd at all.
Would you advocate for only allowing transportation of renewable fuels with means of transportation that use renewable energy themselves? That'd mean throwing away quite a few newly built engines and many more old and perfectly working ones and building new ones ... that'd seem like a waste to me.
Making the shipping industry carbon neutral is of course part of the task .. but according to a quick web search worldwide shipping amounts to ~ 4.5 % of greenhouse gas emissions .. that's only a fraction and not the big chunk that ought to get all the attention.
If you try to put the last step first, the whole thing falls apart.
In that case it might blow your mind the fact that natural gas is shipped in crude oil powered tankers.