Using an external battery on the EcoFlow Pro

I saw this on the YouTube channel Jasonoid. He plugged a LiTime 48V, 100 AH battery into the solar port of an EcoFlow. Essentially, he’s added another 5 KW-H of capacity to his system. Has anyone here done this? Seems like a cheaper way to boost your capacity than buying another smart battery

https://youtu.be/9ODIF2EfsUA?si=j4--RV-ELMxYiqjy