I work with HANA everyday. It stores all its data on disk, ofc it does. How else would it do it? Its loaded to memory as needed.
Tbh, there are much much more important things to criticise about HANA than default settings being unsecure. The very poor performance and serious bugs in SQL impl. The lack of clustering for rowstore tables. The lack of active active support. The lack of ACID. The downtime required for upgrades, typically a week. The incredible cost. The political sillyness.
As you point out, the guides already tell you how to do it right.