In reply to smollett:
It's very unlikely that pedals would be included in the quoted weight. A pair of 105 pedals is 285g, if you have also fitted bottle cages and Garmin/Wahoo mount then you would be getting towards your unaccounted for 500g.
The only way to be sure is as you say, to strip it down and weigh components to work out where the extra mass is. Good advice upthread about tires.
Edit to add, I must have dreamed a poster suggesting tires as something to look at, these are often changed from the original spec due to supply etc and a lot of extra weight could be added to the total if cheaper tires have been used than the build they weighed for their marketing.
Post edited at 20:51