The team led Dr. Madhusudhan had published data on planet K2-18 b in 2023, with detection of Methane, CO2 and even dimethyl sulfide using the JWST.
There were exciting discussions at the time about the possibility of life on K2-18 b, but the data was weak and further study was warranted.
The new announcement is apparently based on additional observations by JWST made in 2024.
As we know, extraordinary claims require extraordinary evidence. Time will tell.