If I'm misreading your comment somehow, please correct me. Maybe I misunderstood something.
This is in contrast to other cloud storage services which might (for example) allow you to save space on your phone by uploading your old photos to the cloud and deleting the local copies.
https://help.backblaze.com/hc/en-us/articles/217664898-What-...
If I really need a long-term cold backup, it costs about half as much yearly (with a half terabyte SSD) to copy the whole thing over to a B2 bucket and get rid of the live backup. That's what I'd do if I were going to Mars.