Green Energy

Correct. That's the main supposed advantage of these vertical axis turbines, in the context of offshore.

... its concept has a simple, robust design with a low centre of gravity, while its moving parts are located close to the water surface, enabling easier, cheaper maintenance.

The lower center of gravity decreases the size of the submerged substructure and therefore also its costs, and there's also the fact a VAWT doesn't need a yaw system.

Main supposed benefit, aside from the supposed windflow benefits, that is:

When set closely interspaced in pairs, VAWTs increase each other’s performance by up to 15%, the UK-based institute said in its press release, triggering much media attention.

The researchers argue that VAWT’s in wind-farm array do not suffer from HAWT-related turbulent wake issues created by the first row, which decrease the output of the rows of turbines behind by up to 40%. Using vertical- rather than horizontal-axis machines would not only eliminate this problem, they suggest, but the VAWTs would actually enhance each other’s performance.

Which is both explained in more detail in the OP article, and most definitely put in question as well(!).

But yeah, costs are probably even more important than that:

...the larger scale of offshore wind turbines and improved materials indicate that VAWT designs may have certain advantages and benefits for floating offshore wind energy installations. For instance, VAWT designs have a lower center of gravity, which would reduce the platform costs. From a systems perspective, that could be a huge breakthrough for floating offshore wind, where the platform is the single largest contributor to the system cost," said Brandon Ennis, Sandia's Wind Energy Technologies Department offshore technical lead. "The turbine represents approximately 65% of the system cost for land-based wind plants, compared to only around 25% for deep-water offshore sites.

There are downsides too, it's a numbers game. That's why I'm curious what will the full large scale test by SeaTwirl in Norway show.

¯\_(ツ)_/¯