First ever cloudy mainframes? IBM offered z/OS as an IaaS for year under the zCloud banner. The only reason they're creating this now is because zCloud was spun off into Kyndryl late last year, leaving a hole in their offerings.
IBM offered a zCloud IaaS for the last few years, but then offloaded it with Kyndryl. There's been production workloads running on it for quite a while now.
Sounds like IBM are just trying to recreate it on their public site after they sold it off.