There is
nothing in the article you linked that explains why "low temperatures and the complex, ever-changing dynamics of sea ice" used to make the region "virtually inaccessible to satellites" but now no longer does.
Further, I did a search using "challenges of satellites in the Southern Ocean" and found no info, rather than plenty of info.
edit: I eventually found the following link which does seem to discuss some challenges, but does not indicate that they have been solved. It certainly does not support the claim that the region is "inaccessible to satellites".
https://www.tandfonline.com/doi/pdf/10.1080/15481603.2023.21...