notice that "typically". basically, those who wrote that felt it's the "right" way of using them. but given all cpus are independent, they may be used independently. i don't have rockpro, but i am sure, linux uses them exactly like i said - independently. or at least it can be configured to use them like that. also you can assign a thread to run only on big or little cores. there is no any prevention in the hardware to use all 6 cores, trust me.
ANT - my hobby OS for x86 and ARM.