Ok, so I think my test will still be at least somewhat effective in showing the effect of veiling flare even though it might not show the localized flare effect (perhaps I could try that in a third test).
It of course makes sense the density range of the tablet will be higher on a glossy surface, but for film testing personally I think we could do with the reduced range of a matte finish. You can't plot a full range film curve from a single exposure of a step tablet anyway, so I'd rather have to do an extra exposure and not have to deal with reflection problems. You have to be careful how you orient the tablet and meter to avoid reflections ruining the test. It is an annoyance.
Apologies to Rafal for hijacking this. I wasn't sure if I should post my questions to this thread or the one I already had going in case nobody was reading it.