The student may understand the topic in a guided setting but not yet know how to choose the first step without support.
Following a worked example and solving a fresh question are different skills. A student who has only ever seen steps demonstrated may understand every line shown, but freeze the moment the wording changes or a step is missing. The exam tests the second skill. Most classroom practice only develops the first. For Add Maths specifically, see why students lose marks in IGCSE Add Maths; the patterns overlap closely.

