Focus-training devices are built around maintaining or restoring engagement with a chosen activity. Memory-training devices instead ask users to encode, retain, and retrieve information. Both require attention, but the critical error occurs at a different point: losing contact with the task is not the same as failing to store or recall its content.
Picture someone rereading a paragraph. If the words were never processed because the mind wandered, return practice addresses the immediate breakdown. If the paragraph was understood yet its details disappear after a delay, an encoding or retrieval approach is more relevant. Observing the error before choosing a device prevents one symptom from standing in for another.