Bread (wholemeal or not makes little difference) will usually raise everyone's blood glucose, it's the large amount of carb in it, plus the relatively large quantity eaten. Being lower than where you started at the +2 hr test following zero carb meals isn't (I think) a problem - it often happens for me.
What we're aiming for is an overall reduction in blood glucose. Carbohydrate in food is digested to glucose, and it therefore makes sense that we should be restricting taking in carbs/glucose. If I have a a zero carb meal - just eggs, or salami and cheese, or a steak, for example, I won't be taking in any carb and shouldn't see any rise in BG as a result. However if there a is no glucose coming in from food I'll be relying on my liver to adjust my blood glucose, by releasing glucose from stores or making new glucose itself, and to trigger bodyfat usage.
Livers are both a bit unpredictable and slow learners, and will usually try to keep our blood glucose round about where it's been most recently. If it's been higher, it will try to get back to those levels. It took mine months to adjust to me being at lower levels.
does that answer your question?