If you forget chemistry, you have an excuse. Once upon a time, I majored in it... so memory lapses make me look bad.
Well, if you're completely wrong, then that makes two of us.

My thoughts were the exact same.
Interesting side note: Pre-DX, I noticed that I felt much better after eating acidic foods... which adds to my wondering how long I was undiagnosed. (I'd had the three polys for a while.)
I've used acid (vinegar, orange, lemon) when boiling poultry into broth. Yes, the acid definitely seems to help break down protein; I presume complex CHO is much the same.
I'm just surprised at how little vinegar apparently has a substantial effect on the spaghetti. When one is used to holding a ~25 mg/dL range after eating, and suddenly ends up 60-120 mg/dL off, it catches one's attention...
I hope it's the vinegar. I can't think of anything else that has changed... and I like my spaghetti, and the good postprandial BG numbers that I usually can turn in.
Mich, the bottle claims 2g CHO per tablespoon. Even if I used 1/4 cup (4 Tbsp.), that would be 8 g... which, for an otherwise-300 g batch, amounts to an error of less than 3%. If I could guesstimate portions and insulin dosing with such precision, I'd be very happy indeed.