Hmm, where's that you've seen? That's interesting... Other half works in the hospital lab and he's never known false positives come up, as either the glucose rate spikes or it doesn't..? (I had a lot of questions when I had mine but was very reassured by the time I went).
I've heard of the other way round though, where it gets missed or develops later after the test - it can be slow for the sugar to rise and therefore second blood doesn't catch it...
It's dull, sure, but in my mind absolutely worth it, I'd hate for problems with insulin production to affect baby's health, and any pregnancy can result in GD whether you've had it before or not...
Besides, a positive would mean extra growth scans and more monitoring so wouldn't necessarily rule out any future birth plans, would depend entirely on baby's growth and your health - often just changing diet slightly is enough to get back to 'normal' levels without medication or birth interventions.