I do get that they are disproportionately represented, and I think the Guardian's suggestions that they possibly "have have something to prove", and are likely to be "more vulnerable to extremist interpretations of key teachings and texts" due to their superficial cultural and religious knowledge intuitively make sense. I just think that's not necessarily something that should be a major focus. Rather than splitting them out by converts vs. non-converts, I'd suggest there are other variables at play that have a stronger correlation. It's much harder to establish a robust metric that looks at social exclusion, political disenfranchisement etc. so I appreciate why people are looking at something more tangible, but they (from what I can tell) are the key drivers - conversion isn't.
However the reality is that in spite of a disproprortionate number of converts buying into the ideology, there are still a substantial amount of non-converts in there - by most reports they're the majority group. A narrow focus on a minority group might allow you to allow to glean a bit more qualitative information from their individual cases but I'm not convinced it wouldn't obscure the big picture. 96% of the British muslim population are non-converts, and 88% of "Homegrown Jihadis" are non-converts (if we take the Guardian's figures as correct). They're proportionately less likely to get sucked into it, and the % difference is statistically significant, but it seems dangerous to focus in on another group when the absolute numbers are still that high.