For your specific example, I think I would have slowed a lot rather than a little, for the following reason:You most correctly assessed things. I needed to get differing input to sort out my own thinking. In the future will slow a little in similar situations. Most cars don't have hazard lights on as they simply feel entitled to park in the bike lane.
I was actually surprised that I kept my avg up because of the strong wind
If a car is on a straight open road, giving absolutely no indication that it's doing anything other than carry on in a straight line, and unless there's little chance it could do anything other than carry on in a straight line... except if the driver has a stroke - or is perhaps giving himself a stroke, then you can probably carry on without slowing.
If a car is approaching a hazard where you think it might do something silly without indication (and you're in the way if it does), then fully expect it to do something silly, perhaps slow a little, and anticipate evasive action being required.
If a car is parked in your lane, especially if it has hazard lights on, and especially if it suddenly starts to make erratic movements into other lanes, then it's probably wise to slow (maybe to a stop), wait for it to finish its faffing about, then carry on cautiously once it's decided what it's doing, and then preferably finished doing it.
While it's nice to maintain your preferred speed when that's the sort of thing that floats your boat, sometimes shoot happens, you log a slightly slower time, and then you hope for better luck next time.