but not answered.

"Why would you need a rust disk for external storage rather than an SSD?"
"Personal Experience"

That is not a useful answer. That's no different than parents who say "because I said so."

MY personal experience is that rust drives are great for long term storage, and are painfully slow for near-term external storage. I do a lot of photography, and there's a LOT of difference between transferring 250+GB of large files over USB to a spinning drive vs an SSD.

SSDs are excellent for external storage, with HDDs as a long term backup. I currently store all my photography in the near term on an external NVMe and back that up every couple weeks to large HDDs overnight, because I don't really care to sit and wait for two hours while large amounts of data are written through a tiny bottleneck.