Eco-Load is a setting being introduced to Spitfire Plugin libraries that purges articulations automatically.
It can be found in the plugin settings, under the interface option.
Eco-Load when enabled only loads the selected techniques into RAM.
When you key switch, or select a new articulation, this will then load into RAM.
Clicking on the Purge button next to Purge Unused in the Preset settings menu (under the ellipsis) will reset the memory usage back to only storing the currently select technique: