It's definitely not a single team in charge of the UX. UX is a centralized department but each team can get UX Managers, UX Designers, and UX Researchers. The headcount for those roles come from each individual organization.

Nowadays there's a workflow to ship new consoles and big features that require UI changes but there are still many consoles built on the legacy design system and designing or improving those is pretty hard. The right decision is to migrate those consoles to the design system but that is a painful process.