They might be right that spinning rust isn't going to be used for online storage due to the energy cost, but that doesn't mean it can't still be useful for offline storage. I'm not buying this.
According to this, JEDEC Solid State Technology Association's standard is that SSDs should be able to retain data for 1 year at 30C. Not great for an archival medium.
Here's a Quora discussion about it: https://www.quora.com/How-long-can-SSD-store-data-without-po...
Vendors will claim much better numbers than this, but the standard isn't very good.