I think it is a mistake to overly generalize about any fanbase. I think most Texans are hoping that bad Flacco shows up instead of good Flacco. As for the improvement of the Texans defense, it isn't just the switch from a 4-3 to 3-4 but also incorporating a ton of new starters on defense and teaching them new VERY new positions. Mario Williams and Connor Barwin were switched to linebacker. Two new safeties. The remaining linemen with new responsibilities. Getting starter snaps from rookies JJ Watt and Brooks Reed. Getting the secondary all on one page with two new free agents. I am blown away at how many changes were made and how good they got so quick. And even though Flacco managed to connect in the first meeting, (one of those "catches" was very sketchy), he got hit a ton. Maybe protection is better now that your line is fixed back up, but maybe not.
But I'm not sure why you are surprised that Texans fans might have questions about which Flacco shows up.
For example.
Yes, the Ravens have always beaten the Texans. Maybe that happens until infinity. I doubt it.