7 hosts in that poc, that is not "at scale"

Scylla can handle 10-100x the load of Cassandra on the same servers. Scale is more than just the number of hosts.

Data density is a thing. If u putting 10tb on a c* host, switching to Scylla doesn’t fix the issues that putting 1pb of data on a host would involve (ie backing that up). Throughput of 100mb of data done in marketing benchmarks are rarely relevant.

Ok, but that's a different issue and nobody is suggesting 1PB of data on a single node as a good idea. The comment was that "scale" is more than just a simple count of nodes. Even if you keep the data the same size, Scylla can handle it with much better performance which is a good enough reason for many to use it.

Since that poc they're using Scylla on hundreds of machines... that's just an old post.