Xiaomi has unveiled MIUI 13 for global audiences, albeit without any notable changes from MIUI 12.5 and MIUI 12.5 Enhanced. MIUI 13 will arrive on 18 devices this quarter, but it will not introduce previously-announced features, such as MiSans font or Google's Material You design language.
https://www.notebookcheck.net/Xiaomi-sets-out-MIUI-13-global-rollout-starting-with-Mi-11-Redmi-Note-10-Xiaomi-11T-and-over-a-dozen-other-devices.595618.0.html
xiaomi is afraid that no one will ever again use their useless theme app thats why they skip new features like material you fonts and so on, that's why they are the only oem that don't allow changing icon shape, a basic android feature from 2018.. not on xiaomi phones
what is the meaning of rollout? the first batch devices at the end of march will be able to use it (at least if everything gors fine) or does it only mean beta stable rolled out release date nit available