For their comparisons, they used the "social cost" of CO2 emissions, I presume a detriment to combustion engined ships, a benefit to battery powered ones? Also they used the "2nd life" of the battery too, batteries that have not been repurposed at any meaningful scale yet?

I'm becoming more skeptical of reports, especially government reports, like this; there's a thumb on the scale toward solutions that are politically favored. Clearly this report was trying to find any way to boost the appearance of EVs.