According to Xiaomi's CEO, it is a heavily modified Android and Vela (Xiaomi's IoT OS based on the open source embedded OS Nuttx) to replace MIUI in all Xiaomi mobile, auto, and intelligent home products.
Unfortunately it works. Consumers are dumb. The HBO show The Wire covered this, the drug dealers were losing customers because of low quality product. They rebranded so they could continue selling the same crap. This tactic works. Comcast did a real life version of this in the US, year after year they were rated as one of the worst ISPs, they rebranded as Xfinity and people seemed to stop complaining.