STM32F10x RTC Clock Source
Yes, and if you use the LSE clock, everything is fine. This blurb is telling you that if you choose an alternate clock source for the RTC, such as HSE or LSI you will NOT be fine.

A lot of applications just need to keep track of runtime, and so don't have a 32k crystal or anything like that to maintain time across power cycles. For THOSE applications, LSI or HSE clock sources are adequate. It sounds like that's not a good way to go for you though.