the ship is ultimately owned by a Japanese company

All the articles I've found say that the ship is chartered/operated by Japanese companies but owned by a British company called Galaxy Maritime Limited. Idk who owns GML, but could be the Israeli.

I think the point is not the direct loss of the ship, but the increase in Maritime insurance if the insurance ghouls think that the Yemenis are going to seize more Westoid ships sailing through Suez. The ultimate goal might be to get Maritime insurers to refuse to insure ships sailing through Suez, which would effectively result in Israel being forced to rely on its own merchant fleet.