OK but why they write "benign optimization landscape devoid of stationary points" instead of "convex" other than "just for show"? In my understanding it's not b

OK but why they write "benign optimization landscape devoid of stationary points" instead of "convex" other than "just for show"? In my understanding it's not better for either audience experts or laymen. For experts it would be more clear to just say convex and they would know the implications, and if someone doesn't know what convex means they probably also aren't going to be on board with 'stationary points'. Also I'm not trying to pick on the authors I'm just trying to answer the question of which specific parts could be seen as 'just for show'.