Sorry for the delay! I talked to the lead chemist, Chris, and Kyle today. The ambient temp, windshield temp, humidity, etc can all affect flash fime. It's likely Part A was already set before you even applied Part B. It can happen very quickly...when it flashes, it's immediately time to move to Part B.
He recommended to avoid this issue in the future, to work quickly and in halves of the windshield (somewhat contrary to the video, yes, so I'll bring that up). As in, open Part A, and immediately apply to half the windshield. As soon as it flashes, which could be in seconds (time will vary), immediately open Part B and apply to the same half. Do not wait. Do not pass go. Do not collect $200. Then, go to other half and do the same thing. Glass Cleaner is your friend to remove residue...once Part A and B are applied, the GC will not remove anything further so use as much as you want/need.
Also, if BG hadn't worked, you can try Sprayable Compound to remove residue that may have streaked.
Hope that helps. If any more questions, let me know and I'll ask...