As someone who works in data centers (L3, Qualys, H5, currently QTS) I've never seen a rack that does only direct to hardware liquid cooling... That's actually insane to think about. Every AIO style rack solution I've seen is designed to be deployed in a traditional hot/cold rack environment and definitely still has air cooling, not to mention they have these big chillers that are basically an entire racks worth of radiators and fans.

When people say "liquid cooled" data centers, we're talking about the heat exchangers for the air system. Every data center I've worked in uses air cooling in a hot side/cold side rack configuration. The differences being how that air is cooled. Most I've worked in use a closed loop refrigerant system. Smaller co-located facilities will use water/air but these aren't generally used for AI, or at least not specifically as they are mostly for smaller businesses that rent a couple racks.

I'm really not sure where this article is getting it's info from or what specific data centers it's talking about.

I've also never heard of a pure "AI" datacenter outside of specialized labs. Most of the datacenters you see popping up in cities are for general commercial use. We don't really dictate what type of hardware and workloads you can and cannot run in your rack. Google/Amazon/Microsoft/Oracle are not building pure AI datacenters, they are building expanded availability zones for edge computing and often lease space from larger datacenters that are geographically advantaged.