IOTL I agree with you, but in an alternate scenario either they, or a similar group, would rise to fill the role of organizing the militias. Maybe the Broederbond creates some kind of armed wing if they choose to live or die with Apartheid. While the SADF is highly effective, which complicates any kind of breakup by itself, militias, specifically Afrikaner nationalist ones, will arise.I think the influence of the AWB is overstated. Even during apartheid they were pretty much considered a bunch of brandy-soaked rednecks (even by most other Afrikaners).
You mighr see Afrikaner militias arise, but they'll probably work more in concert with what is left of the SADF, rather than with the AWB.