Just because it's a made in China or a no brand, and no User Agreement or Privacy Policy?
No. Repeater also does not have a CPU chip that can run an OS and software to capture and transmit your data. That costs money.
If a vendor wants to steal you info, it will, no matter if it has User Agreement or Privacy Policy on paper or anywhere. But as I said, it costs money, and a lot of efforts, not worth it.
A repeater just receive a wifi signal and retransmit it to your wifi devices, it probably can't even reach more than 50ft.
What you should worry is its quality. Why choose a no brand when TP-Link products are already cheap/affordable and have been proven for many years?