Your points, on the whole are very valid, but I’d think that the quoted statement is a little categorical. If African writers on the whole tend to gravitate toward the literary, reading as an activity in itself, divorced from the tyranny of marks and exams ,is mostly geared toward the non-literary genres. We all had our Chase phase, as we did have our Ludlum, Wilbur Smith, Christie, Gardner, et al phases. Guys I knew in school, who didn’t go on to Literature ‘O’ and ‘A’ Levels in my native S/Leone, were highly unlikely to be found reading what would be considered literary outputs.
So if our ‘training’ in reading is/was literary, the practice of reading continues to be non-literary.