Thats not a typo, just confusing it refers to the PRU UART0 pins and not UART0. But yes UART8 is also on those pins. The schematic pin labels does not list all the possible functions for a pin. It would make the labels much too long.
I put together a spreadsheet for the BBAI-64 pin muxing - BBAI-64 pin mux spreadsheet which might be of use.
wkup_uart0 and mcu_uart0 are different. however uart0 on the headers I think is the same as mcu_uart0, justed muxed to different pins.