You can improve in intelligence by generalizing ('My intelligence improved in generality'), or by further investing in what you're good at ('My intelligence improved without improving in generality'). It seems like we could mean two different things by 'generalizing'.

Suppose four skills exist, A,B,C,D; and my skill level can either be low (0), mediocre (1), high (2), or very high (3). If I start off with A=0, B=1, C=2, D=2, then 'generalizing' might mean improving A or B more than I improve C or D. Alternatively, 'generalizing' might mean improving in more skills, rather than in just one. On the former conception, 'raise A to 2' increases my intelligence's generality more than 'raise C to 3 and D to 3'; on the latter conception, the reverse is true. There's plug-the-gaps generalization, where you try to get rid of your weak points; but there's also spread-the-love generalization, where you try to find self-improvements that will impact your problem-solving ability in as diverse a range of problems as possible.

'Qualitative intelligence improvements' seems like a grab-bag for 'all the kinds of intelligence improvements that we don't usually measure in any simple and direct way'. We routinely talk about, e.g., the speed, number, and computing power of computers, in terms of simple numerical values; we don't routinely do the same for computers' language-processing abilities, so that goes in the 'qualitative' bag, at least for the moment. Improving in qualitative intelligence could take almost any form; it seems like a less natural category than 'generality'.