Here is attached an extract of an online training that should be available soon on st.com. It shows the principle of the cube programmer.
To answer your question, partition 0x01 and 0X03 are used to indicate the binary to be used to flash the memory (serial boot). Only trusted boot is supported by the cube Programmer here (so you cannot replace it with basic boot).
More details about programmer and tsv format:
https://wiki.st.com/stm32mpu/wiki/STM32CubeProgrammer
https://wiki.st.com/stm32mpu/wiki/STM32CubeProgrammer_flashlayout
If the memory to flash is an sdcard, there are many alternatives to flash them (here are 2 easy ones):
Note: Basic boot is not a "normal" boot for a product (many features are not available in basic boot). The normal boot is trusted one even if you don't care about security.