Pasta - confusing readings

I am highly intolerant of carbs in general, hence why I have to low carb to keep control. One slice of Burgen bread spikes me, so I know that I have to be so very, very careful of all I eat. Hence why I prepare my menu a day in advance so I know the carb count, and also why I weigh every last little thing I eat - I have to.

groan (only kidding)

No, don't have an explanation for that, though I'm sure it's not a precise science. Of course, you're assuming that you're catching the top of your spike with your reading. It's possible that one or more of the readings is ahead of, or behind, the curve.

I am hyper sensitive to some carbs and less to others of the same grams of carb.

I am one of those who doesn't have processed carbs in any quantity. They take me out of my goal area so I just don't have them.
Would I be prepared to cook just one tablespoon of something anyway? I don't think so as it seems to be a waste of energy to achieve what?
Cauliflower, zucchini, celeriac are my carbs of choice these days when once I had rice or pastas. It is amazing what a difference food habits do to our head space. My husband has been low carbing for about three years now after watching my progress for six months beore being convinced I was on a healthy journey.
I made a very low carb roll/bun (eggs, whey powder, coconut flour and butter) and was delighted with the result and paraded them in front of him, he glanced up from his newspaper and said that he didn't really care if he never ate a 'bread' again in his life. This was they man who could easily demolish a whole crisp bauguette for lunch pre-low carb days!!

If I had three strikes with a food like you did I would not be going there again.